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8/2/2019 T. Kerzenmacher et al- Validation of NO2 and NO from the Atmospheric Chemistry Experiment (ACE)
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Atmos. Chem. Phys., 8, 5801–5841, 2008
www.atmos-chem-phys.net/8/5801/2008/
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.
AtmosphericChemistry
and Physics
Validation of NO2
and NO from the Atmospheric Chemistry
Experiment (ACE)
T. Kerzenmacher1, M. A. Wolff 1, K. Strong1, E. Dupuy2, K. A. Walker1,2, L. K. Amekudzi3, R. L. Batchelor1,
P. F. Bernath4,2, G. Berthet5, T. Blumenstock6, C. D. Boone2, K. Bramstedt3, C. Brogniez7, S. Brohede8,
J. P. Burrows3, V. Catoire5, J. Dodion9, J. R. Drummond10,1, D. G. Dufour11, B. Funke12, D. Fussen9, F. Goutail13,
D. W. T. Griffith14, C. S. Haley15, F. Hendrick9, M. H opfner6, N. Huret5, N. Jones14, J. Kar1, I. Kramer6,
E. J. Llewellyn16, M. Lopez-Puertas12, G. Manney17,18, C. T. McElroy19,1, C. A. McLinden19, S. Melo20, S. Mikuteit6,
D. Murtagh8, F. Nichitiu1, J. Notholt3, C. Nowlan1, C. Piccolo21, J.-P. Pommereau13, C. Randall22, P. Raspollini23,
M. Ridolfi24, A. Richter3, M. Schneider6, O. Schrems25, M. Silicani20, G. P. Stiller6, J. Taylor1, C. Tetard7,
M. Toohey1, F. Vanhellemont9, T. Warneke3, J. M. Zawodny26, and J. Zou1
1Department of Physics, University of Toronto, Toronto, Ontario, Canada
2Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada3Institute of Environmental Physics, Institute of Remote Sensing, Universitat Bremen, Bremen, Germany4Department of Chemistry, University of York, Heslington, York, UK5Laboratoire de Physique et Chimie de l’Environnement, CNRS–Universite d’Orleans, Orleans, France6Forschungszentrum Karlsruhe und Universitat Karlsruhe, Inst. f ur Meteorologie und Klimaforschung (IMK), Karlsruhe,
Germany7Laboratoire d’Optique Atmospherique, Universite des sciences et technologies de Lille, Villeneuve d’Ascq, France8Department of Radio and Space Science, Chalmers University of Technology, Goteborg, Sweden9Belgisch Instituut voor Ruimte-Aeronomie–Institut d’Aeronomie Spatiale de Belgique (IASB-BIRA), Bruxelles, Belgium10Department of Physics & Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada11Picomole Instruments Inc., Edmonton, Alberta, Canada12Instituto de Astrof ısica de Andalucıa, CSIC, Granada, Spain13
Service d’Aeronomie–CNRS, Verrieres-le-Buisson, France14School of Chemistry, University of Wollongong, Wollongong, Australia15Centre for Research in Earth and Space Science, York University, Toronto, Ontario, Canada16Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Saskatchewan, Canada17Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA18New Mexico Institute of Mining and Technology, Socorro, NM, USA19Environment Canada, Downsview, Ontario, Canada20Canadian Space Agency, St Hubert, Quebec, Canada21Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UK22Laboratory for Atmospheric and Space Physics & Department of Atmospheric and Oceanic Sciences, University of
Colorado, Boulder, CO, USA23Istituto di Fisica Applicata “Nello Carrara” (IFAC) del Consiglio Nazionale delle Ricerche (CNR), Firenze, Italy24Dipartimento di Chimica Fisica e Inorganica, Universita di Bologna, Bologna, Italy25Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany26NASA Langley Research Center, Hampton, VA, USA
Received: 4 December 2007 – Published in Atmos. Chem. Phys. Discuss.: 14 February 2008
Revised: 14 July 2008 – Accepted: 9 August 2008 – Published: 8 October 2008
Correspondence to: T. Kerzenmacher
(tobias@atmosp.physics.utoronto.ca)
Published by Copernicus Publications on behalf of the European Geosciences Union.
8/2/2019 T. Kerzenmacher et al- Validation of NO2 and NO from the Atmospheric Chemistry Experiment (ACE)
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5802 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
Abstract. Vertical profiles of NO2 and NO have been
obtained from solar occultation measurements by the At-
mospheric Chemistry Experiment (ACE), using an in-
frared Fourier Transform Spectrometer (ACE-FTS) and
(for NO2) an ultraviolet-visible-near-infrared spectrometer,
MAESTRO (Measurement of Aerosol Extinction in the
Stratosphere and Troposphere Retrieved by Occultation).
In this paper, the quality of the ACE-FTS version 2.2NO2 and NO and the MAESTRO version 1.2 NO2 data
are assessed using other solar occultation measurements
(HALOE, SAGE II, SAGE III, POAM III, SCIAMACHY),
stellar occultation measurements (GOMOS), limb mea-
surements (MIPAS, OSIRIS), nadir measurements (SCIA-
MACHY), balloon-borne measurements (SPIRALE, SAOZ)
and ground-based measurements (UV-VIS, FTIR). Time dif-
ferences between the comparison measurements were re-
duced using either a tight coincidence criterion, or where
possible, chemical box models. ACE-FTS NO2 and NO and
the MAESTRO NO2 are generally consistent with the cor-
relative data. The ACE-FTS and MAESTRO NO2 volumemixing ratio (VMR) profiles agree with the profiles from
other satellite data sets to within about 20% between 25 and
40 km, with the exception of MIPAS ESA (for ACE-FTS)
and SAGE II (for ACE-FTS (sunrise) and MAESTRO) and
suggest a negative bias between 23 and 40 km of about 10%.
MAESTRO reports larger VMR values than the ACE-FTS.
In comparisons with HALOE, ACE-FTS NO VMRs typi-
cally (on average) agree to ±8% from 22 to 64 km and to
+10% from 93 to 105 km, with maxima of 21% and 36%,
respectively. Partial column comparisons for NO2 show that
there is quite good agreement between the ACE instruments
and the FTIRs, with a mean difference of +7.3% for ACE-
FTS and +12.8% for MAESTRO.
1 Introduction
This is one of two papers describing the validation of NO y
species measured by the Atmospheric Chemistry Experiment
(ACE) through comparisons with coincident measurements.
The total reactive nitrogen, or NOy, family consists of ac-
tive nitrogen, NOx (NO+NO2), and all oxidized nitrogen
species, including NO3, HNO3, HNO4, ClONO2, BrONO2
and N2O5. The ACE-Fourier Transform Spectrometer (ACE-FTS) measures all of these species, with the exception of
NO3 and BrONO2, while the Measurement of Aerosol Ex-
tinction in the Stratosphere and Troposphere Retrieved by
Occultation (ACE-MAESTRO, referred to as MAESTRO in
this paper) measures NO2. The species NO2 and NO are
two of the 14 primary target species for the ACE mission. In
this study, the quality of ACE-FTS version 2.2 nitrogen diox-
ide (NO2) and nitric oxide (NO) and MAESTRO version 1.2
NO2 are assessed prior to their public release. A compan-
ion paper by Wolff et al. (2008) provides an assessment of
the ACE-FTS version 2.2 nitric acid (HNO3), chlorine ni-
trate (ClONO2) and updated version 2.2 dinitrogen pentoxide
(N2O5). Validation of ACE-FTS version 2.2 measurements
of nitrous oxide (N2O), the source gas for NOy, is discussed
by Strong et al. (2008).
NO2 and NO are rapidly interconverted and closely linked
through photochemical reactions in the atmosphere. As NOx,
they have a maximum lifetime of 10 to 50 h in the strato-sphere between 20 and 50 km under midlatitude equinox con-
ditions (Dessler, 2000). The NOx gas phase catalytic cycle
destroys odd oxygen in the stratosphere, while NO2 and NO
also have important roles determining the polar ozone bud-
get.
Remote sensing measurements of NO2 and NO have been
performed since the early 1970s (e.g. Murcray et al., 1968;
Ackermann and Muller, 1972; Brewer et al., 1973; Burkhardt
et al., 1975; Fontanella et al., 1975; Noxon, 1975). Satel-
lite instruments have been regularly measuring these species
since the launch of Nimbus-7 in 1979, which carried the
Stratospheric and Mesospheric Sounder (SAMS) for NO(Drummond et al., 1980) and the Limb Infrared Monitor
of the Stratosphere (LIMS) for NO and NO2 (Gille et al.,
1980). There was a visible light spectrometer on board the
Solar Mesosphere Explorer (SME) spacecraft, which also
made early measurements of NO and NO2 (Mount et al.,
1984). The launch of the Upper Atmosphere Research Satel-
lite (UARS) in 1991 provided measurements from the Im-
proved Stratospheric and Mesospheric Sounder (ISAMS)
(Taylor et al., 1993), the Cryogenic Limb Array Etalon Spec-
trometer (CLAES) (Roche et al., 1993) and the HALogen
Occultation Experiment (HALOE) (Russell et al., 1993).
The ACE mission builds on the heritage of a number
of previous solar occultation missions, including the At-mospheric Trace MOlecule Spectroscopy (ATMOS) instru-
ment (Abrams et al., 1996; Gunson et al., 1996; Newchurch
et al., 1996; Manney et al., 1999), which flew on four
Space Shuttle flights between 1985 and 1994. The three
Stratospheric Aerosol and Gas Experiment instruments,
SAGEI (McCormick et al., 1979; Chu and McCormick,
1979, 1986), SAGE II (Mauldin et al., 1985) and SAGEIII
(SAGE ATBD Team, 2002) all used ultraviolet-visible (UV-
VIS) solar occultation to measure NO2, as did the second
Polar Ozone and Aerosol Measurement (POAMII) (Glac-
cum et al., 1996) and POAMIII (Lucke et al., 1999; Ran-
dall et al., 2002). The Improved Limb Atmospheric Spec-trometers (ILAS) I and II were infrared solar occultation in-
struments that also measured NO2 (e.g. Sasano et al., 1999;
Nakajima et al., 2006; Irie et al., 2002; Wetzel et al., 2006).
In addition to the ACE instruments, there are currently two
instruments in orbit measuring NO2 using the occultation
technique: SCIAMACHY (SCanning Imaging Absorption
spectroMeter for Atmospheric CHartographY), doing solar
occultation measurements, (which is its secondary measure-
ment mode) (Bovensmann et al., 1999) and the stellar oc-
cultation instrument GOMOS (Global Ozone Monitoring by
Atmos. Chem. Phys., 8, 5801–5841, 2008 www.atmos-chem-phys.net/8/5801/2008/
8/2/2019 T. Kerzenmacher et al- Validation of NO2 and NO from the Atmospheric Chemistry Experiment (ACE)
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T. Kerzenmacher et al.: Validation of NO2 and NO from ACE 5803
the Occultation of Stars) (Kyrola et al., 2004, and references
therein).
Space-based measurements of NO2 are also being made
using several other techniques. The Global Ozone Mon-
itoring Experiment GOME (Burrows et al., 1999), SCIA-
MACHY (Bovensmann et al., 1999), GOME-2 (Callies et al.,
2004), and the Ozone Monitoring Instrument (OMI) (Lev-
elt et al., 2006) all retrieve NO2 total columns from nadir-viewing observations at visible wavelengths. Also using
this spectral range for NO2, but in limb-scattering mode,
is the Optical Spectrograph and Infra-Red Imager System,
or OSIRIS, (Llewellyn et al., 2004) and SCIAMACHY
(Bovensmann et al., 1999) in limb mode. The Michelson
Interferometer for Passive Atmospheric Sounding (MIPAS)
detects both NOx species and is the only instrument besides
ACE-FTS that is currently measuring stratospheric NO from
orbit (Fischer and Oelhaf, 1996; Fischer et al., 2008). Recent
validation studies of NO2 have been performed by Brohede
et al. (2007a) for OSIRIS and Wetzel et al. (2007) for MIPAS
Environmental Satellite (Envisat) operational data; the latterincluded a comparison with the ACE-FTS v2.2 data. In addi-
tion, measurements of NO2 by GOMOS, MIPAS and SCIA-
MACHY, all on Envisat, were compared by Bracher et al.
(2005a).
In this paper, we assess the quality of the ACE-FTS ver-
sion 2.2 NO2 and NO data and the MAESTRO version 1.2
NO2 data through comparisons with available coincident
measurements. The paper is organized as follows. In Sect. 2,
the ACE mission and the retrievals of these two species by
ACE-FTS and MAESTRO are presented. Section 3 describes
all of the satellite, balloon-borne and ground-based instru-
ments used in this study. The validation methodology and the
use of a chemical box model to account for the diurnal vari-
ability of NO2 and NO are discussed in Sect. 4. In Sect. 5,
the results of vertical profile and partial column comparisons
for NO2 are given, while Sect. 6 focuses on the results of the
NO and NOx comparisons. Finally, the results are summa-
rized and conclusions regarding the quality of the ACE NO2
and NO data are provided in Sect. 7.
2 The Atmospheric Chemistry Experiment
The ACE satellite mission, in orbit since 12 August 2003,
carries two instruments, the ACE-FTS (Bernath et al., 2005)and a dual spectrometer, MAESTRO (McElroy et al., 2007).
Both instruments record solar occultation spectra, ACE-FTS
in the infrared and MAESTRO in the UV-VIS-near-infrared,
from which vertical profiles of atmospheric trace gases, tem-
perature and aerosol extinction are retrieved. The SCISAT
spacecraft is in a circular orbit at an altitude of 650 km, with
a 74◦ inclination angle (Bernath et al., 2005), providing up
to 15 sunrise and 15 sunset solar occultations per day. The
choice of orbital parameters results in coverage of the trop-
ics, midlatitudes and polar regions with an annually repeat-
-90 -60 -30 0 30 60 90
Latitude
0
2
4
6
8
10
12
F r e q u
e n c y i n %
Fig. 1. Sampling frequency of 11,111 ACE satellite measurements
(February 2004 to December 2007) using 5◦latitude bins.
ing pattern, and a sampling frequency that is greatest over the
Arctic and Antarctic (see Fig. 1). The primary scientific ob-
jective of the ACE mission is to understand the chemical and
dynamical processes that control the distribution of ozone in
the stratosphere and upper troposphere, particularly in the
Arctic (Bernath et al., 2005; Bernath, 2006, and references
therein).
In previous studies McHugh et al. (2005) compared ACE-
FTS v1.0 NO2 to HALOE v19 NO2 and found a low bias
of 0 to 10% from 22 to 35km, and a high bias of 0 to
50% below 22 km. Comparisons between HALOE v19 and
ACE-FTS v1.0 NO data were described by McHugh et al.(2005), who found that ACE-FTS NO was 10 to 20% smaller
than HALOE from 25 to 55 km. Large uncertainties were
present from 65 to 90 km, and ACE-FTS NO was approxi-
mately 50% smaller than HALOE above 90 km. ACE-FTS
and MAESTRO NO2 profiles have been compared with data
from POAMIII and SAGE III (Kar et al., 2007) and partial
columns have been compared with those retrieved using the
Portable Atmospheric Research Interferometric Spectrome-
ter for the InfraRed (PARIS-IR), a ground-based adaptation
of ACE-FTS and other ground-based spectrometers during
the spring 2004 to 2006 Canadian Arctic ACE validation
campaigns (Kerzenmacher et al., 2005; Fraser et al., 2008;
Sung et al., 20081; Fu et al., 2008). ACE-FTS NOx profileshave been used in high energy particle precipitation studies
(Rinsland et al., 2005; Randall et al., 2007).
1Sung, K., Strong, K., Mittermeier, R. L., Walker K. A., Fu, D.,
Kerzenmacher, T., Fast, H., Bernath, P., F., Boone, C. D., Daffer,
W. H., Drummond, J. R., Kolonjari, F., Loewen, P., MacQuarrie, K.,
and Manney, G. L.: Ground-based column measurements at Eureka,
Nunavut, made using two Fourier transform infrared spectrometers
in spring 2004 and 2005, and comparison with the Atmospheric
Chemistry Experiment, in preparation, 2008.
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8/2/2019 T. Kerzenmacher et al- Validation of NO2 and NO from the Atmospheric Chemistry Experiment (ACE)
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5804 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
0.0 0.1 0.2 0.3uncertainty [ppbv]
10
20
30
40
50
h
e i g h t [ k m ]
(a)
0 5 10 15 20relative uncertainty [%]
0 5 10 15 20relative uncertainty [%]
(b) 036563679371337503790381238343853387538903905
390939193913390839063894384036590
# o f o c c u l t a t i o n s
Fig. 2. MAESTRO uncertainties for NO2 using all available data
from 2005. Profiles are shown for the median (solid), and 16th
and 84th percentiles (dotted) of the (a) absolute and (b) relative
uncertainties.
2.1 ACE-MAESTRO
MAESTRO is based on the Meteorological Service of
Canada’s SunPhotoSpectrometer (McElroy, 1995; McElroy
et al., 1995) that flew on the Space Shuttle in 1992 and was
used as part of the NASA ER-2 stratospheric chemistry re-
search program (McElroy et al., 2007). It incorporates two
instruments: the UV-VIS instrument that covers the range
285 to 565 nm with a full width at half intensity resolution
of 1.5 nm and the visible-near-infrared instrument that mea-
sures spectra in the 515 to 1015 nm range with a resolution of
2.0 nm. For the retrievals, GOME flight model NO2 (221 K)and O3 (202 K) absorption cross-sections (Burrows et al.,
1998; Burrows et al., 1999) are used. The spectral fits are
performed across a wide range of wavelengths, from 420 to
545 nm in the UV and 530 to 755 nm in the visible, and are
modelled at a wavelength spacing of 0.1 nm.
NO2 is fit using a differential optical absorption spec-
troscopy method (e.g. Platt, 1994; Platt and Stutz, 2008),
combined with an iterative Chahine (1970) relaxation inver-
sion algorithm. A detailed description of how the retrievals
are performed can be found in McElroy et al. (2007). No di-
urnal corrections were made to the retrieved VMR profiles.
Kar et al. (2007) present errors for the NO2 profiles. Insummary, there is an estimated uncertainty due to fitting er-
rors of <5% between 20 and 40 km, which is found by propa-
gating the estimated uncertainty through the spectral retrieval
process. Additionally there is a systematic error of about 2%
due to uncertainties in NO2 cross sections and 5 to 10% sys-
tematic error due to not accounting for temperature effects in
the NO2 cross sections. The error due to temperature effects
in the O3 cross sections is smaller than 1%. Figure 2 shows
the median of the MAESTRO fitting error uncertainties for
all retrieved NO2 profiles over the year 2005. The retrieval
program propagates estimated uncertainty through the spec-
tral retrieval process. This is a good proccess for the linear
inversion algorithm but does not work well for the Chahine
method. For the version 1.2 retrievals, the Chahine method
is used, and the uncertainties are propagated with a simpli-
fied algorithm. These uncertainties are, therefore, not very
accurate but they provide some relative estimate and serve
as a rough guide to the relative uncertainties of the MAE-STRO measurements. The median relative uncertainties in-
crease exponentially with altitude for NO2. The magnitude
of the relative uncertainties is a function of the retrieval er-
rors and the VMR profiles. The median relative uncertainties
are <5% from 20 to 40 km, increasing to 18% at 49 km.
The MAESTRO data products are reported on two vertical
grids: VMR as a function of tangent altitude and VMR as a
function of altitude interpolated onto a 0.5-km grid with the
same interpolation method used in the optical model. The
full width at half maximum slit size results in an instrument
field-of-view of 1.2 km in the vertical and approximately 35
(UV-VIS) and 45 km (VIS-near infrared) in the horizontalfor a tangent altitude of 22 km. During an occultation, the
signal comes only from the solar disk and the signal extent
in the horizontal is then 25 km (McElroy et al., 2007). The
altitude resolution of MAESTRO profiles is in the range 1
to 2 km. This was concluded by Kar et al. (2007) based
on comparisons of MAESTRO observations with coincident
ozonesonde profiles. For the MAESTRO analysis, pressure-
temperature profiles are needed. For the version 1.2 MAE-
STRO data, these are taken from the ACE-FTS retrieval. The
altitude-time sequence from the ACE-FTS measurements is
used for altitude assignment in the MAESTRO retrievals.
The comparisons in this work are made with version 1.2 of
the MAESTRO data on the 0.5-km grid.
2.2 ACE-FTS
ACE-FTS measures atmospheric spectra between 750 and
4400 cm−1 (2.2 to 13µm) at a resolution of 0.02 cm−1
(Bernath et al., 2005). From these spectra, pressure, temper-
ature and VMR profiles of over 30 trace gases are retrieved as
functions of altitude. Typical signal-to-noise ratios are more
than 300 from ∼900 to 3700 cm−1. The instrument field-of-
view (1.25 mrad) corresponds to a maximum vertical resolu-
tion of 3 to 4 km (Boone et al., 2005). The vertical spacing
between consecutive 2-second ACE-FTS measurements de-pends on the satellite’s orbit geometry during the occultation
and can vary from 1.5 to 6 km. The altitude coverage of the
measurements extends from the cloud tops to between ∼100
and 150 km.
The approach used for the retrieval of VMR profiles and
other details of the ACE-FTS processing are described by
Boone et al. (2005). A brief description of the retrieval pro-
cess is given here. A non-linear least squares global fitting
technique is employed to analyze selected microwindows
(0.3 to 30cm−1 wide portions of the spectrum containing
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T. Kerzenmacher et al.: Validation of NO2 and NO from ACE 5805
0.0 0.2 0.4 0.6 0.8statistical fitting error [ppbv]
20
30
40
50
h
e i g h t [ k m ]
(a)
-50 0 50relative stat. fitting error [%]
-50 0 50relative stat. fitting error [%]
(b)
4176
4323
4331
4331
43254320
4312
4301
4175
3659
2694
1641
957
39770
# o f o c c u l t a t i o n s
Fig. 3. ACE-FTS statistical fitting errors for NO2 using all available
data from 2005. Profiles are shown for the median (solid), and 16th
and 84th percentiles (dotted) of the (a) absolute and (b) relative
statistical fitting errors.
spectral features for the target molecule). Prior to perform-
ing VMR retrievals, pressure and temperature as a function
of altitude are determined through the analysis of CO 2 lines
in the spectra. Forward model calculations employ the spec-
troscopic constants and cross section measurements from the
HITRAN 2004 line list (Rothman et al., 2005).
For the purpose of generating calculated spectra (i.e. per-
forming forward model calculations), quantities are interpo-
lated from the measurement grid onto a standard 1-km grid
using piecewise quadratic interpolation. The comparisons in
this work use the VMRs on the 1-km grid. Retrieved quanti-ties are determined at the measurement heights.
The retrieval for NO2 employs 21 microwindows ranging
from 1581 to 1642 cm−1, covering an altitude range of 13
to 58 km. There are minor interferences from various iso-
topologues of H2O in these microwindows, but no interfer-
ers are retrieved. For NO2, the wavenumber ranges for the
microwindows remained the same between versions 1.0 and
2.2, but the altitude limits changed. The lower altitude limit
was raised from 10 km in version 1.0 to 13 km in version 2.2
to avoid saturation of the spectral region that occurred at low
altitudes in tropical occultations. The upper altitude limit
was raised from 45 km in version 1.0 to 58 km in version 2.2to capture enhancements in NO2 at high altitudes during po-
lar spring (e.g. Rinsland et al., 2005; Randall et al., 2007).
For occultations with no enhancements at high altitudes, the
top portion of the retrieved NO2 VMR profile will be mostly
fitting noise. The precision of the ACE-FTS NO2 VMRs
is defined as the 1σ statistical fitting errors from the least-
squares process, assuming a normal distribution of random
errors (Boone et al., 2005).
Version 2.2 ACE-FTS microwindows for NO range from
1842.9 to 1923.5 cm−1 covering an altitude range from 15 to
0.1 1.0 10.0 100.0 1000.0statistical fitting error [ppbv]
20
40
60
80
100
h
e i g h t [ k m ]
(a)
-50 0 50relative stat. fitting error [%]
-50 0 50relative stat. fitting error [%]
(b)
3742446644744474447444764476447644764476
44764476447744774477447544724467446344574442442743801936
# o f o c c u l t a t i o n s
Fig. 4. Same as Fig. 3 but for ACE-FTS NO.
110 km. A total of 20 microwindows were used for the re-
trieval of NO. For NO, the upper altitude limit for retrievalswas lowered from 115 km in version 1.0 to 110 km in ver-
sion 2.2, and the lower altitude limit was raised from 12
to 15 km. Two NO microwindows from version 1.0, in the
wavenumber range 1820 to 1830 cm−1, were in the overlap
region between the MCT and InSb detectors. As a result,
these two microwindows suffered from elevated noise and
were therefore removed from version 2.2 processing. Five
new microwindows were added for version 2.2 NO retrievals.
For version 1.0, there were four interfering species for NO
retrievals (H2O, CO2, O3 and N2O). For version 2.2, the mi-
crowindow altitude ranges were selected such that there was
only one interfering species (O3).
The other interferers were fixed to the results of previousretrievals. The NO VMR profile has orders of magnitude
larger VMR values at high altitudes (upper mesosphere and
thermosphere) compared to low altitudes. The retrieved NO
VMR profiles often exhibit a negative spike in the transition
region between large and small VMR. This unphysical result
is a consequence of insufficient altitude sampling in the re-
gion where the NO VMR profile goes through a minimum.
Another known issue in the ACE-FTS version 2.2 NO data
set occurs at low altitudes (below about 25 km). Small, neg-
ative VMR values are often retrieved in this altitude region.
Preliminary investigations suggest that neglecting diurnal ef-
fects in the NO retrievals may be the cause of these negativeVMR values at low altitudes. No diurnal effect corrections
were made to the retrieved VMR profiles for either NO or
NO2.
Figures 3 and 4 show the statistical fitting errors for the
ACE-FTS NO2 and NO profiles, respectively. These er-
rors are calculated as the square root of the diagonal ele-
ments of the covariance matrix used in the least squares fit-
ting procedure. If the measurement errors are normally dis-
tributed and one ignores correlations between the parameters,
this represents the 1σ statistical fitting errors. The median
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T. Kerzenmacher et al.: Validation of NO2 and NO from ACE 5807
3.1.2 SCIAMACHY, GOMOS and MIPAS on Envisat
The European Space Agency (ESA) Envisat mission was
launched on 1 March 2002, carrying three instruments
dedicated to atmospheric science: SCIAMACHY, GOMOS
and MIPAS. Currently, extension of the mission until 2013
is under consideration. Envisat is in a quasi-polar, sun-
synchronous orbit at an altitude of 800 km, with an inclina-tion of 98.6◦, a descending node crossing time of 10:00 and
an ascending node crossing at 22:00 (local time).
SCIAMACHY is a passive moderate-resolution UV-VIS-
near-infrared imaging spectrometer. Its wavelength range is
240 to 2380 nm and the resolution is 0.2 to 1.5 nm. SCIA-
MACHY observes the Earth’s atmosphere in nadir, limb and
solar/lunar occultation geometries and provides column and
profile information of atmospheric trace gases of relevance to
ozone chemistry, air pollution, and climate monitoring issues
(Bovensmann et al., 1999; Gottwald et al., 2006). The pri-
mary measurements during daytime are alternate nadir and
limb measurements.SCIAMACHY solar occultation measurements are per-
formed every orbit between 49◦ N and 69◦ N depending on
season. Although from the instruments’ point of view, the
sun rises above the horizon, the local time at the tangent
point corresponds to a sunset event. In southern latitudes
(40◦ S to 90◦ S) SCIAMACHY also performs lunar occul-
tation measurements, depending on visibility and phase of
the moon (Amekudzi et al., 2005). The SCIATRAN version
2.1 radiative transfer code (Rozanov et al., 2005) is used for
forward modeling and retrieval. An optimal estimation ap-
proach with Twomey-Tikhonov regularization is used to fit
NO2 in the spectral window from 425 to 453nm simulta-
neously with ozone (524 to 590 nm) at the spectral resolu-tion of the instrument. A detailed algorithm description can
be found in Meyer et al. (2005). Recent validation results
are given in Amekudzi et al. (2007) and updated for NO2 in
Bramstedt et al. (2007). Precise tangent height information
is derived geometrically using the sun as a well-characterized
target (Bramstedt et al., 2007).
SCIAMACHY nadir measurements provide atmospheric
NO2 columns with good spatial coverage, providing a large
number of coincidences at all seasons for comparison with
ACE measurements. Here, we use the University of Bre-
men scientific NO2 product v2.0, which is similar to the
GOME columns described in Richter et al. (2005) withoutthe normalisation necessary to correct for a diffuser plate
problem in the GOME instrument. Briefly, the NO2 columns
are retrieved with the Differential Optical Absorption Spec-
troscopy (DOAS) method in the wavelength interval 425 to
450 nm and corrected for light path enhancement using ra-
diative transfer calculations based on the stratospheric part
of the US standard atmosphere. When comparing SCIA-
MACHY columns and ACE measurements, three problems
arise. First, the time of measurement is different as Envisat
is in a morning orbit and most nadir measurements are not
performed during twilight. This time difference has to be
accounted for explicitly by correcting for the diurnal varia-
tion of NO2 (see Fig. 6). Second, the diurnal effect will lead
to a positive bias in the ACE partial columns. Finally, the
SCIAMACHY columns include tropospheric NO2, which
can be large in polluted situations. While polluted measure-
ments have been removed from the data set used, the tropo-
spheric background is included, which is of the order of 0.3to 0.7×1014 molec/cm2 depending on location and season.
GOMOS is a stellar occultation experiment (Kyrola et al.,
2004, and references therein). The instrument is a grating
spectrometer capable of observing about 100 000 star oc-
cultations per year in different UV-VIS-near-infrared spec-
tral ranges with a vertical sampling better than 1.7 km be-
tween two consecutive acquisitions. Global coverage can be
achieved in about three days, depending on the season of
the year and the available stars. The precision of GOMOS
is strongly influenced by both star magnitude and star tem-
perature, which impact the signal-to-noise ratio in the useful
spectral range. This is also influenced by the obliquity of the occultations, which does not allow a complete correction
of the star scintillation produced by atmospheric turbulence.
GOMOS can sound the atmosphere at different local solar
times depending on the star position.
MIPAS is a limb-sounding emission Fourier transform
spectrometer operating in the mid-infrared spectral region
(Fischer and Oelhaf, 1996; Fischer et al., 2008). Spec-
tra are acquired over the range 685 to 2410 cm−1 (14.5
to 4.1µm), which includes the vibration-rotation bands of
many molecules of interest. MIPAS operated from July 2002
to March 2004 at its full spectral resolution of 0.025 cm−1
(0.05 cm−1 apodized with the strong Norton and Beer (1976)
function). MIPAS observes the atmosphere during day andnight with daily coverage from pole to pole and thus pro-
vides trace gas distributions during polar night. Within its
full-resolution standard observation mode, MIPAS covered
the altitude range from 6 to 68 km, with tangent altitudes
every 3 km from 6 to 42 km, and further tangent altitudes
at 47, 52, 60, and 68 km, generating profiles spaced ap-
proximately every 500 km along the orbit. MIPAS passes
the equator in a southerly direction at 10:00 local time 14.3
times a day. During each orbit, up to 72 limb scans are
recorded. In March 2004, operations were suspended follow-
ing problems with the interferometer slide mechanism. Op-
erations were resumed in January 2005 with a 35% duty cy-cle and reduced spectral resolution (0.0625 cm−1; apodized
0.089 cm−1). By December 2007 a duty cycle of 100% had
again been reached.
There are two MIPAS data products available for the
comparisons. The MIPAS IMK-IAA (Institut f ur Meteo-
rologie und Klimaforschung–Instituto de Astrofısica de An-
dalucıa) data used here are vertical profiles of NO2 and NOx
(i.e. the sum of NO2 and NO), which were retrieved with
the dedicated scientific IMK-IAA data processor (von Clar-
mann et al., 2003a,b) from spectra recorded in the standard
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5808 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
observation mode in the period February to March 2004. Re-
trieval strategies considering non-local thermodynamic equi-
librium (non-LTE) effects, error budget and altitude reso-
lution for the species under investigation are reported in
Funke et al. (2005). Here, we use data versions NO 9.0
and NO2 9.0, which include several retrieval improvements,
such as: i) the use of log(VMR) instead of VMR in the re-
trieval vector, ii) revised non-LTE parameters for NO2, andiii) jointly-fitted VMR horizontal gradients at constant lon-
gitudes and latitudes. For NO retrievals, a revised set of
microwindows is applied, which allows NO to be measured
down to altitudes of about 15 km. The estimated precision,
in terms of the quadratic sum of all random errors, is better
than 1 ppbv for NO, at an altitude resolution of 4 to 7 km.
The accuracy, derived by quadratically adding the errors due
to uncertainties in spectroscopic data, temperature, non-LTE
related parameters, and horizontal gradients to the measure-
ment noise error, varies between 0.6 and 1.8 ppbv. The pre-
cision, accuracy and altitude resolution of the NO2 retrieval
are estimated to be 0.2 to 0.3 ppbv, 0.3 to 1.5 ppbv and 3.5 to6.5 km, respectively. At the VMR peak height, the estimated
accuracy is 5 to 10% for NO2 and 10 to 20% for NO.
The second data product is the MIPAS ESA operational
product (v4.62). The Level-1b processing of the data,
including processing from raw data to calibrated phase-
corrected and geolocated radiance spectra, is performed by
ESA (Kleinert et al., 2007). For the high-resolution mis-
sion, ESA has processed pressure, temperature and the six
key species H2O, O3, HNO3, CH4, N2O and NO2. The algo-
rithm used for the Level 2 analysis is based on the optimized
retrieval model (Raspollini et al., 2006; Ridolfi et al., 2000).
3.1.3 OSIRIS on Odin
OSIRIS, launched in February 2001, is currently in orbit on
the Odin satellite (Llewellyn et al., 2004). It is in a circular,
sun-synchronous, near-terminator orbit (18:00 local time as-
cending node) at an altitude of 600 km. OSIRIS measures
sunlight scattered from the Earth’s limb between 280 and
800 nm at a resolution of 1 nm and for tangent heights be-
tween 7 and 70 km.
A comprehensive description of the NO2 retrieval algo-
rithm is provided in Haley et al. (2004), with the most re-
cent improvements given in Haley and Brohede (2007). In
summary, NO2 profiles are retrieved by first performing aspectral fit on OSIRIS radiances between 435 and 451 nm.
The slant column densities (SCDs) derived from this fit are
then inverted to number density profiles from 10 to 46 km,
at a vertical resolution of about 2 km using the optimal esti-
mation technique (Rodgers, 2000). Version 2.3/2.4 OSIRIS
NO2 has been extensively validated against satellite occul-
tation instruments (after mapping the OSIRIS profiles from
their solar zenith angle to 90◦) (Brohede et al., 2007a). These
comparisons were recently repeated with the most recent
NO2 product, version 3.0 (Haley and Brohede, 2007), and
it is this version that is used in the comparisons here (avail-
able from http://osirus.usask.ca/ ). The validation studies con-
cluded that the OSIRIS random/systematic uncertainties are
16/22% from 15 to 25 km, 6/16% from 25 to 35 km and
9/31% from 35 to 40 km.
3.2 SPIRALE balloon measurements in the Arctic
SPIRALE (SPectroscopie Infra-Rouge d’Absorption par
Lasers Embarques) is a balloon-borne instrument op-
erated by the Laboratoire de Physique et Chimie de
l’Environnement (LPCE) (Centre National de la Recherche
Scientifique (CNRS)-Universite d’Orleans) and routinely
used at all latitudes, in particular as part of European satellite
validation campaigns (e.g. Odin and Envisat). This instru-
ment is an absorption spectrometer with six tunable diode
lasers and has been previously described in detail by Moreau
et al. (2005). In brief, it can perform simultaneous in situ
measurements of about ten different chemical species from
about 10 to 35 km height, with a high sampling frequency of about 1 Hz, thus enabling a vertical resolution of a few meters
depending on the ascent rate of the balloon. The diode lasers
emit in the mid-infrared spectral region (from 3 to 8µm) with
beams injected into a multipass Heriott cell located under the
gondola and largely exposed to ambient air. The cell (3.5-m
long) is deployed during the ascent when pressure is lower
than 300 hPa. The multiple reflections obtained between the
two cell mirrors give a total optical path of 430.78m.
Species concentrations are retrieved from direct infrared
absorption, by fitting experimental spectra with spectra cal-
culated using the HITRAN 2004 database (Rothman et al.,
2005). Specifically, the ro-vibrational lines at 1598.50626
and 1598.82167 cm−1 were used for NO2. Measurementsof pressure (provided by two calibrated and temperature-
regulated capacitance manometers) and temperature (ob-
tained from two probes made of resistive platinum wire)
aboard the gondola allow the species concentrations to be
converted to VMR. Uncertainties in these parameters have
been found to be negligible with respect to the other un-
certainties discussed below. The global uncertainties in the
VMRs have been assessed by taking into account the ran-
dom errors and the systematic errors, and combining them
as the square root of their quadratic sum. The two im-
portant sources of random errors are the fluctuations of the
laser background emission signal and the signal-to-noise ra-tio. These error sources are the main contributions for NO 2,
giving a total uncertainty for the flight used in this work
of 50% at the lowest altitude (23.64 km) where it was de-
tectable (>20 pptv), rapidly decreasing to 20% at 23.83 km
(with a VMR of 32 pptv), and even to 6% above 24.28 km
height. Between 17.00 and 23.60 km height, NO2 was unde-
tectable (<20 pptv, with uncertainties of about 50 to 200%).
With respect to these errors, systematic errors in spectro-
scopic data (essentially molecular line strength and pres-
sure broadening coefficients) are considered to be negligible.
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T. Kerzenmacher et al.: Validation of NO2 and NO from ACE 5809
The measurements were performed near Kiruna, Sweden
(67.6◦ N and 21.55◦ E) (see Fig. 5).
3.3 UV-VIS balloon and ground-based instruments.
Vertical profiles of NO2 from three UV-VIS instruments have
been used in this study. They were retrieved from ground-
based measurements by a SAOZ (Systeme d’Analyse parObservation Zenitale) spectrometer from CNRS, deployed in
Vanscoy, Canada and by a DOAS system from Belgisch In-
stituut voor Ruimte-Aeronomie–Institut d’Aeronomie Spa-
tiale de Belgique (IASB/BIRA) in Harestua, Norway. Addi-
tionally, there were NO2 profiles obtained during flights of a
SAOZ balloon instrument in France and Niger.
The SAOZ instrument is a UV-VIS spectrometer exist-
ing in two configurations: a ground-based version for the
measurement of O3 and NO2 columns at sunrise and sun-
set by looking at sunlight scattered at zenith (Pommereau
and Goutail, 1988a,b), and a balloon version for the mea-
surement of the same species by solar occultation during theascent of the balloon and at twilight from float altitude (Pom-
mereau and Piquard, 1994). The ground-based instrument,
part of the Network for the Detection of Atmospheric Com-
position Change (NDACC), has been compared several times
to other UV-VIS systems (Vandaele et al., 2005, and refer-
ences therein). There are about 20 ground-based SAOZ in-
struments deployed at latitudes from Antarctica to the Arctic;
data from these instruments have been used since 1988 for
the validation of O3 and NO2 column satellite measurements
by TOMS, GOME, SCIAMACHY and OMI (e.g. Lambert
et al., 1999, 2001), whilst the profiles from the balloon ver-
sion have been also used for the validation of profiles mea-
sured by SAGE II, HALOE, POAM II and III, ILAS II, MI-PAS and GOMOS (e.g. Irie et al., 2002; Wetzel et al., 2007).
The ground-based SAOZ data used in the present work
are from a SAOZ deployed in Vanscoy (Canada, 52.02◦ N,
107.03◦ W) during the MANTRA (Middle Atmosphere Ni-
trogen TRend Assessment) campaign (Strong et al., 2005)
in September 2004, from which profiles have been retrieved
by the optimal estimation technique (Melo et al., 2005).
The SAOZ balloon data are from one midlatitude flight at
Aire-sur-l’Adour, France (43.71◦ N, 0.25◦ W) in May 2005
and from three tropical flights in Niamey, Niger (13.48◦ N,
2.15◦ E) in August 2006. The other ground-based instru-
ment used in this study is the IASB-BIRA DOAS spectrome-ter, also part of NDACC, operating permanently at Harestua,
Norway (60◦ N, 11◦ E) (Roscoe et al., 1999) (see Fig. 5). It
has been validated during several NDACC comparison cam-
paigns (Vandaele et al., 2005, and references therein).
The retrieval of NO2 profiles from ground-based UV-VIS
measurements is based on the dependence of the mean scat-
tering height on solar zenith angle (Preston et al., 1997). The
fitting window used for NO2 is 425 to 450 nm. The IASB-
BIRA NO2 profiling algorithm is described in detail in Hen-
drick et al. (2004). In brief, it employs the optimal estima-
Fig. 5. Locations of the ground-based and balloon instruments used
in the comparisons. From the north, FTIRs in red: Ny-Alesund,
Kiruna, Bremen, Toronto, Izana, Wollongong, UV-VIS in blue:
Harestua, Vanscoy and balloon launches in green: Kiruna, Aire-
sur-l’Adour, Niamey.
tion method (Rodgers, 2000) and the forward model consists
of the radiative transfer model UVspec/DISORT (Mayer and
Kylling, 2005; Hendrick et al., 2007) coupled to the IASB-
BIRA stacked box photochemical model PSCBOX (Hen-
drick et al., 2004). The inclusion of a photochemical model
in the retrieval algorithm allows the effect of the rapid vari-
ation of the NO2 concentration along the light path to be re-
produced. It also makes profile retrieval possible at any solar
zenith angle. Estimations of the error budget and information
content are given in Hendrick et al. (2004). In the ground-
based DOAS NO2 observations at Harestua there are about2.5 independent pieces of information and the vertical reso-
lution is 8 to 10 km at best. In order to reduce the smoothing
error associated with the difference in vertical resolution be-
tween ground-based and ACE profiles in the comparisons,
ACE-FTS and MAESTRO profiles are degraded to the verti-
cal resolution of the ground-based retrievals. This is done by
convolving the ACE profiles with the ground-based DOAS
averaging kernels (Hendrick et al., 2004).
3.4 Ground-based Fourier transform infrared spectrome-
ters
In addition to the vertical profile and the UV-VIS partial col-
umn comparisons, ACE-FTS NO and NO2 measurements
have been compared with partial columns retrieved from
solar absorption spectra recorded by ground-based Fourier
Transform Infrared Spectrometers (FTIRs). NO was pro-
vided by five and NO2 by six stations that are part of
NDACC. These instruments make regular measurements of
a suite of tropospheric and stratospheric species.
Table 1 lists the stations that participated, their locations
and the coincidence criteria used. Toronto and Wollongong
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5810 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
Table 1. List of the FTIR stations that provided data for the analyses (Sect. 5.3 and Sect. 6.3). The latitude and longitude of each station
are provided, together with the altitude above sea level in meters (m.a.s.l.). The coincidence criteria used in this study are indicated for each
station in column 4. References describing the stations, measurements and analyses are given in column 5.
Station Coordinates Alt. [m.a.s.l.] Coincidence criteria Reference
Ny Alesund, Svalbard 78.9◦ N, 11.9◦ E 20 ±24 h, 1000 km Notholt et al. (1997)
Kiruna, Sweden 67.8◦ N, 20.4◦ E 419 ±12 h, 500 km Blumenstock et al. (2006)Bremen, Germany 53.1◦ N, 8.9◦ E 27 ±24 h, 1000 km Buchwitz et al. (2007)
Toronto, Canada 43.7◦ N, 79.4◦ W 174 ±48 h, 1000 km Wiacek et al. (2007)
Izana, Canary Islands 28.3◦ N, 16.5◦ W 2367 ±24 h, 1000 km Schneider et al. (2005)
Wollongong, Australia 34.5◦ S, 150.9◦ E 30 ±24 h, 1000 km Paton-Walsh et al. (2005)
use Bomem DA8 FTIRs with resolutions of 0.004 cm−1 and
optical path differences of 250 cm, whereas the other sta-
tions use Bruker FTIRs (Ny Alesund and Kiruna: 120 HR,
Bremen: 125 HR and Izana: 120 M until end of 2004,
then 125 HR). All Bruker instruments have a resolution of
0.004 cm−1, but those shown here normally use 0.005 cm−1
for better signal-to-noise ratio. More information about the
instruments, the retrieval methodologies and the measure-
ments made at each of these sites can be found in the ref-
erences provided in Table 1. The participating stations cover
latitudes from 34.5◦ S to 78.9◦ N, and provide measurements
from the subtropics to the polar regions in the Northern
Hemisphere (see Fig. 5). There is only one station for which
we have measurements in the Southern Hemisphere. Days
for which coincident FTIR data were available for compari-
son with ACE are as follows:
– Ny Alesund: NO2: 23 and 28 September 2004, 14 and
16 March 2005, 26 September 2005; NO: 14 and 16March 2005.
– Kiruna: NO2: 27 and 29 October 2004, 25 Jan-
uary 2005, 1, 2 and 7 February 2005, 18, 19, 23
and 25 May 2005, 5 February 2006, 20 March 2006,
18 May 2006; NO: 27 and 29 October 2004, 7 February
2005, 18, 19 and 25 May 2005, 10 November 2005, 5
February 2006, 18 May 2006.
– Bremen: NO2: 2 and 3 September 2004, 24 March
2005, 13 February 2006, 8, 9 and 12 May 2006, 3, 25,
26 and 27 July 2006, 28 November 2006.
– Toronto: NO2: 23 and 29 July 2004, 2 June 2005, 1 and
2 September 2005, 3 and 5 May 2006, 31 August 2006;
NO: 23 and 29 July 2004, 29 July 2005, 3 May 2006,
29 July 2006, 31 August 2006.
– Izana: NO2: 5 and 30 April 2005, 1, 2 and 30 August
2005 and 20 October 2005; NO: 3 August 2004, 5 and
30 April 2005, 1, 2 and 30 August 2005.
– Wollongong: NO2: 1 March 2005, 3 November 2005,
20 and 21 August 2006, 31 October 2006 and 1 Novem-
ber 2006; NO: 3 and 4 October 2004, 1 March 2005, 19
April 2005, 20 and 21 August 2006, 31 October 2006
and 1 November 2006.
The FTIR measurements require clear-sky conditions and
take measurements all year round during daylight. Onlycloud-free measurements are included in the comparisons.
The data used here were analyzed using either the SFIT2
retrieval code (Pougatchev and Rinsland, 1995; Pougatchev
et al., 1995; Rinsland et al., 1998) or PROFFIT92 (Hase,
2000). Both algorithms employ the optimal estimation
method (Rodgers, 2000) to retrieve vertical profiles from a
statistical weighting between a priori information and the
high-resolution spectral measurements. The retrieval codes
have been compared and it was found that the differences
were less than ∼1% (Hase et al., 2004). Averaging kernels
calculated as part of this analysis quantify the information
content of the retrievals, and can be used to smooth the ACE
profiles, which have higher vertical resolution.For NO2, there are typically 0.1 to 2 Degrees Of Free-
dom for Signal (DOFS, equal to the trace of the averaging
kernel matrix) and for NO about one DOFS is found in the
altitude range coincident with ACE-FTS measurements and
about half a DOFS greater for the total columns.
Given this coarse vertical resolution, we compare partial
columns rather than profiles. All sites used spectroscopic
data from HITRAN 2004, with the exception of Kiruna and
Izana (HITRAN 1996 for NO2 and HITRAN 2001 for NO).
Comparisons of FTIR retrievals using HITRAN 1996 and
2004 showed that NO2 total and partial columns are about
2% lower when using HITRAN 1996.Other information required for the retrievals, such as a pri-
ori profiles and covariances, treatment of instrument line-
shape, and atmospheric temperature and pressure are opti-
mized for each site as appropriate for the local conditions.
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T. Kerzenmacher et al.: Validation of NO2 and NO from ACE 5811
4 Validation approach
4.1 Comparison methodology
The comparisons shown in this work use ACE data from
21 February 2004 (the start of the ACE Science Operations
phase) through to 28 March 2007. The coincidence criteria
needed to search for correlative measurements were deter-mined by considering temporal and spatial variability. The
statistical significance of the results for the satellite compar-
isons was also considered. Ground-based and balloon mea-
surements were considered coincident with the ACE mea-
surements when they were within 1000 km and 24 h of each
other. This resulted in cases, notably for balloon compar-
isons, where only one ACE coincidence profile was avail-
able. The value that was used in searching for coincidences
is the location for each ACE occultation, which is defined as
the latitude, longitude and time of the tangent point at 30 km
(calculated geometrically). We do not expect a seasonal bias
with solar occultation instruments, therefore seasonal depen-
dencies were not studied here.
Because NO2 and NO are short-lived species, a chemi-
cal box model (described in Sect. 4.2) was used for all but
the solar occultation comparisons and the MIPAS-IMK/IAA
NOx comparisons, to correct for the time difference in satel-
lite comparisons. For the ground-based, aircraft and bal-
loon measurements, box model scaling was applied when the
measurements were not taken at the same solar zenith angle.
For the balloon measurements, profiles obtained within
36 h and 1000 km of ACE were used. For the FTIR compar-
isons, measurements that occurred within 24 h and 1000 km
of ACE occultations were compared, with the exception of
Kiruna where tighter criteria (12 h and 500 km) were used.These relaxed criteria were necessary to obtain a reasonable
number of ACE coincidences for each station (between 5
and 72). In cases where several FTIR measurements from
a site were available for one ACE occultation or vice versa,
all pairs were considered.
Table 1 lists the FTIR stations and Table 2 summarizes all
other correlative data sets, comparison periods, temporal and
spatial coincidence criteria, and number of coincidences.
The satellite VMR profiles and the SAOZ-balloon VMR
profiles all have vertical resolutions that are similar to those
of the ACE instruments, and so no averaging kernel smooth-
ing was applied to these data. These correlative profiles werelinearly interpolated on to the 1-km ACE-FTS or the 0.5-
km MAESTRO altitude grid. The balloon-borne SPIRALE
VMR profile was obtained at significantly higher vertical
resolution than the ACE instruments, and so was convolved
with a triangular function having full width at the base equal
to 3 km and centered at the tangent heights of each occul-
tation for ACE-FTS and with a Gaussian function having
full width at half maximum equal to 1.7 km for MAESTRO.
This approach simulates the smoothing effect of the limited
resolution of the ACE instruments, as discussed by Dupuy
et al. (2008). The resulting smoothed profiles were then
interpolated onto the 1-km grid for ACE-FTS and the 0.5-
km grid for MAESTRO. Finally, for the comparisons with
the ground-based FTIR and UV-VIS measurements, which
have significantly lower vertical resolution, the ACE profiles
were smoothed by the appropriate FTIR or UV-VIS aver-
aging kernels to account for the different vertical sensitiv-
ities of the two measurement techniques. The method of Rodgers and Connor (2003) was followed and Eq. (4) from
their paper was applied, using the a priori profile and the av-
eraging kernel matrix of the FTIR and the UV-VIS instru-
ments (see Sect. 5.3). Partial columns over specified altitude
ranges were then calculated for the ACE instruments and the
FTIRs or the UV-VIS instruments and used in the compar-
isons. Additionally, the UV-VIS profiles were compared to
the smoothed profiles from the ACE instruments.
Pairs of vertical VMR profiles from ACE (both FTS and
MAESTRO) and each validation experiment (referred to as
VAL in text and figures below) were identified using the ap-
propriate temporal and spatial coincidence criteria. The re-sults of the vertical profile comparisons will be shown be-
low, with some modifications for the GOMOS comparisons
(Sect. 5.1.3), the single profile comparisons (SPIRALE and
SAOZ; Sect. 5.2) and the FTIR and UV-VIS partial column
comparisons (Sects. 5.3 and 5.4).
(a) The mean profile of the ensemble for ACE and the
mean profile for VAL are plotted as solid lines with the stan-
dard deviations on each of these two profiles, ±1σ , as dotted
lines, in panel (a) of the comparison figures discussed below.
The uncertainty in the mean is calculated as σ(z)/√ N(z)
(where N(z) is the number of points used to calculate the
mean at a particular altitude) and is included as error bars
on the lines in panel (a). Note: in some cases, these error
bars, as well as those in panels (b) and (c) (see below) may
be small and difficult to distinguish.
(b) The mean profile of the absolute differences,
ACE−VAL is plotted as a solid line in panel (b) of the com-
parison figures below, and the standard deviation in the distri-
bution of this mean difference, ±1σ as dotted lines. The term
absolute here refers to differences of the compared VMR val-
ues and not to absolute values in the mathematical sense. The
differences are calculated for each pair of profiles at each al-
titude, and then averaged to obtain the mean absolute differ-
ence at altitude z:
abs(z)=1
N(z)
N(z)
i=1
[ACEi(z) − VALi(z)] (1)
where N(z) is the number of coincidences at z, ACEi(z) is
the ACE (FTS or MAESTRO) VMR at z for the ith coin-
cident pair, and VALi(z) is the corresponding VMR for the
validation instrument. Error bars are also included in these
figures. For the statistical comparisons involving multiple
coincidence pairs (the satellite and UV-VIS profile compar-
isons), these error bars represent the uncertainty in the mean.
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5812 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
Table 2. Summary of the correlative data sets for the instruments used in the statistical and individual profile comparisons with ACE-FTS
and MAESTRO NO2 and ACE-FTS NO. All values are for NO2 comparisons unless noted for NO or NOx, SR is sunrise and SS is sunset.
Instrument Comparison Comparison Vertical range C oincidence Number of
(retrieval version) period location and resolution criteria coincidences
HALOE 2004/07/04– 66◦ N, 60◦ N 20–50 kma ±2 h, 36
(version 19) 2005/08/15 & 49◦ S at 2 km 500 km
SAGE II 2004/08/09– 65◦ N, 21◦ N 20–50 km ±2 h, 148 SR / 17 SSb
(version 6.2) 2005/05/04 & 14◦ S at 2 km 500 km 126c
SAGE III 2004/02/22– 59◦ S – 20–50 km ±2 h, 776
(version 3.0) 2005/12/05 82◦ N at 1 km 500 km
POAM III 2004/03/16– 85◦ S – 20–46 km ±2 h, 295
(version 4.0) 2005/11/27 69◦ N at 1 km 500 km
SCIAMACHY solar occs 2004/03/21– 49◦ N – 16–40 km ±2 h, 372b
(version 2.5) 2007/03/28 69◦ N at 3–5 km 500 km 377c
SCIAMACHY nadir 2004/02/21– 85◦ S – total column same day 4457b
(version 2.0) 2007/02/26 85◦ N 200 km 4366c
GOMOS 2004/04/06– 72◦ S – 14–50 km ±12 h, 6285
(IPF 5.00) 2005/12/08 80◦ N at 2–3 km 500 km
MIPAS ESA 2004/02/21– 20◦ N – 25–46 km ±6 h, 84
(ESA v4.62) 2004/03/26 85◦ N at 3 km 300 kmOSIRIS 2004/02/21– 82◦ S – 12–43 km ±2 h, 543b
(version 3.0) 2006/12/31 82◦ N at 2 km 500 km 524c
MIPAS IMK-IAAd 2004/02/22– 20◦ N– 12–70 km ±18 h, 493
(version 9.0) 2004/03/25 85◦ N at 3.5–6.5 km 1000 km
SPIRALE 2006/01/20 67.6◦ N, 15–26 km 13 h, 1
21.55◦ E at several m 413 km
SAOZ 2005/05/07 & 13.48◦ N, 2.15◦ E 13–28 km +12 d, 4
(balloon) 2006/08/07 – 43.71◦ N, 0.25◦ W at 1 km 1000 km
2006/08/19
UV-VIS Harestua 2004/03/22– 60.20◦ N, 13–37 km same day 13 SR /15 SSb
(DOAS) 2005/09/01 12.80◦ E at 8–10 km 750 km 6 SR / 11 SSc
SAOZ 2004/09/01– 52.02◦ N, 15–37 km ±24 h, 5
(ground-based) 2004/09/06 107.03◦
W at 5 km 1000 km
a Value given for NO2 comparisons. For the ACE-FTS comparison with NO, 20 to 108 km was used.b Number of coincidences for ACE-FTS.c Number of coincidences for MAESTRO.d Comparisons with NOx from ACE-FTS only.
(c) Panel (c) of the comparison figures presents the mean
profile of the relative differences. This mean relative differ-
ence is defined, as a percentage, using:
rel(z)
= 100%×1
N(z)
N(z)
i=1
ACEi(z)
−VALi(z)
MEANi(z) (2)
where MEANi(z) = [ACEi(z) + VALi(z)]/2 is the mean of
the two coincident profiles at z for the ith coincident pair.
(d) The relative standard deviations on each of the ACE
and VAL mean profiles calculated in step (a) are given in
panel (d), with the number of coincident pairs given as a
function of altitude on the right-hand y-axis for the statistical
comparisons.
For single profile comparisons (SPIRALE, SAOZ), error
bars represent the combined random error for all panels. The
ACE-FTS data products include only statistical fitting errors,
while MAESTRO provides an estimate of relative uncertain-
ties (as described in Sect. 2). No systematic errors are avail-
able, therefore the error bars for the single profile compar-
isons are very small. They cannot be compared directly with
the total errors of the single profile instruments.
4.2 Diurnal mapping using a chemical box model
In Fig. 6, we present a typical example of the modelled tem-
poral evolution of the NO2 concentration in the equatorial
region together with the ACE-FTS and GOMOS local so-
lar time at six different altitudes using the photochemical
box model described by Prather (1997) and McLinden et al.
(2000). This highlights an obstacle faced in the validation
of species that experience diurnal variations when there are
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T. Kerzenmacher et al.: Validation of NO2 and NO from ACE 5815
to 50 km, where the mean absolute differences are around
−0.2 ppbv, but mean relative differences are greater than
40%. The absolute differences at 50 km have a mean differ-
ence of −0.2 ppbv, but most of the points lie above 0 ppbv. So
the large negative differences are skewing the result. The me-
dian does give +0.2ppbv. Relative differences at 50 km have
a mean of 41.2% and a median of 41.3%, so the mean rel-
ative difference is probably more meaningful than the meanabsolute difference. But this carries with it the caveat that
the mixing ratios at this altitude are very small, so even large
percent differences are not very significant in terms of the ac-
tual measurements. Examination of the ACE-FTS and MAE-
STRO data at 50 km shows that the negative absolute differ-
ences come from the many large MAESTRO VMRs caused
by scatter in the data.
From the NO2 profiles, partial columns can be calculated
for both ACE-FTS and MAESTRO. These have been cal-
culated over the range 14.5 to 46.5 km, used for the SCIA-
MACHY nadir comparisons in Sect. 5.1.6, and for different
height ranges shown in Table 3 for all the FTIR comparisonsin Sect. 5.3. Figures 8 and 9 show the scatter plots of the par-
tial columns of the ACE-FTS and MAESTRO used for these
comparisons. They indicate that there is very good agree-
ment, with MAESTRO providing larger column amounts
than the ACE-FTS. Overall there is a very good correlation
(r∼0.97) with the intercept near zero and the slope ∼0.91 in
both scatter comparisons.
It should be noted that the MAESTRO measurements are
known to have occasional timing errors of up to one second
with respect to the ACE-FTS measurements. Since the
MAESTRO retrievals use the tangent heights retrieved for
ACE-FTS and these are imported as a tangent height versus
time table, this can lead to an offset of up to a few kilometers
in the MAESTRO tangent heights, resulting in VMR profiles
that can be smaller or larger than those retrieved from ACE-
FTS or the comparison instrument (Manney et al., 2007).
This problem affects approximately 6% of the v1.2 MAE-
STRO profiles. It is possible to screen out most of these
outliers on a statistical basis, but that has not been done in
this comparison. The inclusion of these data in the analy-
sis is probably responsible for much of the excess variance
in the MAESTRO data as compared to that of similar data
sets (e.g. SAGE III). Additionally, because of the shape of
the NO2 distribution, the effect is larger at high altitudes and
the positive deviations contribute more on average than thenegative ones. As a result, the problem also has an impact on
the bias between MAESTRO and other data sets. This issue
is still under investigation and has not yet been resolved.
5.1.2 NO2 from solar occultation instruments: HALOE,
SAGE II, SAGEIII, POAM III and SCIAMACHY
In this section, NO2 measurements from ACE-FTS and
MAESTRO are compared with solar occultation observa-
tions from HALOE, SAGE II, SAGEIII, POAMIII and
0 2 4 6 8NO2 VMR [ppbv]
10
20
30
40
50
h e i g h t [ k m ]
ACE-FTSHALOE
(a)
-4 -2 0 2 4ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
20 40 60 80σ [%]
(d)
3636363636363636363636363636363636363636363636353530242016125
# o f c o i n c i d e n c e s
Fig. 10. (a) Mean profiles for all measurements by ACE-FTS (solid
red) and HALOE (solid blue). Dotted lines are the profiles of stan-
dard deviations (σ ) of the distributions, while error bars (often too
small to be seen) represent the uncertainty in the mean (σ/√ N ).
(b) Mean differences (solid) between ACE-FTS and HALOE for all
coincidences. Dotted lines represent the standard deviation of the
distribution of the differences while error bars represent the uncer-tainty in the mean difference. (c) Mean percent differences (solid)
between ACE-FTS and HALOE relative to the mean of the two in-
struments, for all coincidences. Dotted lines represent the standard
deviation of the distribution of the differences while error bars rep-
resent the uncertainty in the mean difference. The range ±20% is
highlighted in yellow. (d) Standard deviations of the distributions
(σ ) relative to the mean NO2 VMR at each altitude, for all coinci-
dent events, for ACE-FTS (red) and HALOE (blue). The number of
the coincidences is indicated on the right-hand y-axis.
SCIAMACHY. The comparisons of MAESTRO data with
POAM III and SAGE III were done by Kar et al. (2007) andwill not be repeated here. Instead, a short summary of their
results will be given.
The comparisons with HALOE, SAGE II, SAGE III and
POAM III were carried out separately for sunrise and sunset
events. Only in the case of SAGE II were the sunrise/sunset
differences significantly larger than the average differences
themselves. Thus, comparisons shown below combine sun-
rise and sunset data for HALOE, SAGE III and POAM III,
but separate these data for SAGEII. For the MAESTRO com-
parison the combined sunrise/sunset dataset is shown. SCIA-
MACHY observes only sunset events, therefore the compar-
ison is limited to sunset.For the HALOE, SAGE II, SAGE III and POAM III com-
parisons, the coincidence criteria were chosen so that the
ACE measurements are within 500 km and 2 h of the correl-
ative observation. Thus, differences due to diurnal variations
in NO2 should be minimized. Comparisons with HALOE
occurred primarily in the northern polar region summer,
and with SAGE II primarily in the Northern Hemisphere
spring. A large number of coincidences with POAM III and
SAGE III occurred in the northern polar vortex season, where
the measurements could exhibit substantial variability. The
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5816 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
0 2 4 6 8NO2 VMR [ppbv]
10
20
30
40
50
h e i g h t [ k m ]
MAESTROHALOE
(a)
-4 -2 0 2 4ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
20 40 60 80σ [%]
(d)
373737373737
3737373737373737373737373737373737373636343130218
# o f c o i n c i d e n c e s
Fig. 11. Same as Fig. 10 but for MAESTRO (black) and HALOE
(blue).
0 2 4 6 8NO2 VMR [ppbv]
10
20
30
40
50
h e i g h t [ k m ]
ACE-FTSSAGE II
(a)
-4 -2 0 2 4ACE-val [ppbv]
sunrise (148)sunset (17)
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
20 40 60 80σ [%]
(d)
1551571591581591601621651651651651651651651651651651651631591491391331281181008361423521
# o f c o i n c i d e n c e s
Fig. 12. Same as Fig. 10, but for ACE-FTS and SAGE II. The results
for sunrise–sunrise (blue) and sunset–sunset (purple) comparisonsare presented separately in the difference plots.
SCIAMACHY comparisons are all in northern midlatitudes.
Figures 10 to 17 show the results of the statistical compar-
isons between the ACE instruments and HALOE, SAGE II,
SAGE III, POAM III and SCIAMACHY. For the results of
the comparison of MAESTRO with SAGE III and POAM III,
the reader is referred to Fig. 8a and b and Fig. 9a and b of Kar
et al. (2007), respectively, and the summary plot in Sect. 7 of
this paper.
Over the altitude range investigated, all instruments showthat NO2 has a smooth VMR profile with a broad peak be-
tween 30 and 35 km. Profile-to-profile variations, as mea-
sured by the standard deviations of the distributions, are gen-
erally similar in the ACE-FTS data set to those measured by
the other instruments. A notable difference is that ACE-FTS
variations are significantly smaller than SAGE II from 40 to
45 km (Fig. 12d) and than SAGE III above 45 km (Fig. 14d).
MAESTRO shows generally larger variability than ACE-
FTS, especially above 35 km. As noted above, the standard
deviations for ACE-FTS and MAESTRO shown in panels (d)
0 2 4 6 8NO2 VMR [ppbv]
10
20
30
40
50
h e i g h t [ k m ]
MAESTROSAGE II
(a)
-4 -2 0 2 4ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
20 40 60 80σ [%]
(d)
1191201231231221241241261241241201181171161151151131121081059890868381817975685639
# o f c o i n c i d e n c e s
Fig. 13. Same as Fig. 10, but for MAESTRO (black) and SAGE II
(blue). Sunrise and sunset observations were combined.
0 2 4 6 8NO2 VMR [ppbv]
10
20
30
40
50
h e i g h t [ k m ]
ACE-FTSSAGE III
(a)
-4 -2 0 2 4ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
20 40 60 80σ [%]
(d)
727752775776776776776776776776775775775775774774774774770758732666591452334241181120873518
# o f c o i n c i d e n c e s
Fig. 14. Same as Fig. 10 but for ACE-FTS and SAGE III.
are significantly larger in the POAM III and SAGE III com-
parisons, consistent with the fact that these coincidences are
predominantly at high latitudes during the vortex season.
Differences of ACE-FTS with respect to HALOE are
within about ±15% from 20 to 45 km, with a suggestion of
an ACE-FTS low bias of about 10 to 15% from 24 to 36 km.
A positive bias relative to HALOE increases above 40 km to
a maximum of 40% at 49 km (Fig. 10). MAESTRO shows
similar differences, relative to HALOE: there is agreement
to within about ±15% from 22 to 42 km, with a suggestion of a MAESTRO low bias of about 10 to 15% from 24 to 41 km.
There is, however, a negative bias above 45 km of up to 55%
for MAESTRO, and a similar but more pronounced high bias
than that of ACE-FTS below 22 km (Fig. 11). This could be
a feature of the HALOE data.
Differences of ACE-FTS above 40 km, with respect to
SAGE II, are in the opposite direction, with ACE-FTS lower
than SAGEII by more than 50% from 47 to 50 km. For
sunrise comparisons, ACE-FTS NO2 is higher than SAGE II
by 12 to 38% from 20 to 43 km. ACE-FTS sunsets agree with
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0 2 4 6 8NO2 VMR [ppbv]
10
20
30
40
50
h e i g h t [ k m ]
ACE-FTSPOAM III
(a)
-4 -2 0 2 4ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
20 40 60 80σ [%]
(d)
244278285283267
25324828128929429429529529529229329229429228327125923521019016500000
# o f c o i n c i d e n c e s
Fig. 15. Same as Fig. 10 but for ACE-FTS and POAM III.
SAGE II sunset events to within 13% from 20 to 42 km, with
a low bias throughout most of this altitude range (Fig. 12).
Since none of the other comparisons suggest a large ACE-FTS positive bias, nor a significant ACE-FTS sunrise/sunset
bias, we conclude that this is an artifact of the SAGE II sun-
rise/sunset bias (Randall et al., 2005b). Differences of MAE-
STRO with respect to SAGE II are plotted for sunset and sun-
rise occultations together (Fig. 13). It can be seen that these
differences are very similar to the ACE-FTS sunrise compar-
isons. From 20 to 35 km, MAESTRO is higher than SAGE II
by 15 to 30%. MAESTRO is much lower than SAGE II
above 42 km.
ACE-FTS NO2 is lower than SAGE III NO2 above 43 km,
consistent with the SAGE II comparisons at these altitudes,
but in the opposite direction to the HALOE comparisons.
From 20 to 44 km, ACE-FTS agrees with SAGE III to within
14%, with a low bias from 24 to 40 km (Fig. 14). MAESTRO
shows good agreement with SAGE III (within ±16%) in the
range 25 to 40 km (Fig. 8a of Kar et al., 2007). The VMRs
reported by MAESTRO are consistently lower than those of
SAGE III above approximately 27 km, with maximum differ-
ences of up to −16% around 36 km.
Differences between ACE-FTS and POAM III are within
13% from 25 to 44 km, with negative values approaching
40% below 25 km (Fig. 15). Results for MAESTRO are sim-
ilar below 25 km, with a low bias compared to POAM III
(of about −25% at 23 km). Above 25 km, the MAESTRO–
POAM III differences remain mostly within ±20% and de-crease with increasing altitude, with mean values of +12%
at 27 km to about −24% around 40 km (Fig. 9a of Kar et al.,
2007). Unlike all the other solar occultation instruments con-
sidered in this study, HALOE NO2 has been corrected for the
diurnal effect. This may explain the larger ACE VMRs rela-
tive to HALOE below 25 km because of retrieval errors due
to concentration gradients along the scattering/absorption
paths (see Sect. 4.2).
0 2 4 6 8NO2 VMR [ppbv]
10
20
30
40
50
h e i g h t [ k m ]
ACE-FTSSCIAMACHY
(a)
-4 -2 0 2 4ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
20 40 60 80σ [%]
(d)
372372372372372372372372372372372372372372372372372372372372372372372372
# o f c o i n c i d e n c e s
Fig. 16. Same as Fig. 10 but for ACE-FTS and SCIAMACHY oc-
cultations.
0 2 4 6 8NO2 VMR [ppbv]
10
20
30
40
50
h e i g h t [ k m ]
MAESTROSCIAMACHY
(a)
-4 -2 0 2 4ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
20 40 60 80σ [%]
(d)
377377377377377377377377377377377377377377377377377377377377377377377377377
# o f c o i n c i d e n c e s
Fig. 17. Same as Fig. 10 but for MAESTRO (black) and SCIA-MACHY occultations (blue).
For SCIAMACHY comparisons, 372 coincidences were
found for ACE-FTS and 377 for MAESTRO because only
ACE data that extended from at least 16 to 39 km were used.
Only ACE sunset data were used. In this case, the ACE
data were interpolated onto the SCIAMACHY 1-km grid.
The SCIAMACHY retrieval gives concentrations in number
density, and has no pressure and temperature measurements.
Therefore, the coincident ACE-FTS temperature and pres-
sure profiles were used to calculate the VMR values from theSCIAMACHY profiles.
Figures 16 and 17 show the results of the comparison
between SCIAMACHY and the ACE instruments. Be-
low 20 km, ACE-FTS is higher than SCIAMACHY. From
20 to 39 km, the agreement is within 12% with a pos-
itive bias between 22 and 25km and a negative bias
elsewhere. The results are comparable to the comparisons
with POAM III, only with smaller discrepancies. MAESTRO
measures higher NO2 than SCIAMACHY everywhere. The
agreement is within 12% between 20 km and 40 km. Below
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5818 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
1e7 3e7 1e8 3e8 1e9 3e910
15
20
25
30
35
40
45
50
NO2
[cm−3
]
z [ k m ]
ACE
GOMOS
1e7 3e7 1e8 3e8 1e9 3e910
15
20
25
30
35
40
45
50
NO2
[cm−3
]
z [ k m ]
ACE
GOMOS
−100−75−50−25 0 25 50 75 10010
15
20
25
30
35
40
45
50
∆ [%]
z [ k m ]
100*(ACE−GOMOS)/GOMOS
Fig. 18. Left: Uncorrected ACE-FTS and GOMOS weighted me-
dian profiles (thick lines) with the 16th and 84th percentiles (thin
lines). Middle: Diurnal scaling has been taken into account. Right:
Weighted median of the differences () between ACE-FTS and
GOMOS. Note: the relative median difference is calculated with
respect to the GOMOS median profile.
20 km, at low VMRs in the stratosphere, the differences grow
to more than 100% at 16 km.
Although there are inconsistencies in the solar occultation
comparisons, taken together, and considering previous vali-
dation of the correlative measurements, they suggest that the
ACE-FTS and the MAESTRO NO2 measurements are accu-
rate to within 15% or better in the altitude range from 20 to at
least 40 km, with SAGE II being the exception. Comparisons
among the correlative measurements themselves, as well asbetween the correlative measurements ACE-FTS and MAE-
STRO, lead to inconclusive results for altitudes above about
40 km.
5.1.3 GOMOS stellar occultation NO2 measurements
For the GOMOS comparison, 6865 profiles, of which 1812
are GOMOS dark limb events (at local night), were used with
a time window of 12 h and a distance of 500 km, which is
approximately the effective optical path length at the 30-km
tangent altitude.
Weighted medians were used for the ACE-FTS compar-
isons instead of means for the reasons described by Dupuyet al. (2008). Briefly, when comparing a large number of ver-
tical profiles for two experiments, there might be altitudes
missing, leading to a variable statistical significance of the
data, and there might be outliers that severely contaminate
the data set. The dispersion of the data can then be estimated
by taking the difference of the 84th and 16th percentiles of
this distribution, which corresponds to the standard devia-
tions, σ , in the analysis of a Gaussian distribution.
A second difficulty arises with the co-location criterion.
By shrinking the co-location window in time and space, the
number of events decreases and the result of the compari-
son is hardly statistically significant. On the other hand, in-
creasing the window may introduce systematic biases due to
spatio-temporal NO2 inhomogeneities.
In the left panel of Fig. 18, we present the weighted me-
dian (with the 16th and 84th percentiles) NO2 number den-
sity profiles for GOMOS and ACE-FTS, which were calcu-lated from the VMR profiles. These data consist of 6865
co-located occultations and are not corrected for the diurnal
NO2 evolution. The GOMOS densities are larger due to a
large number of GOMOS dark limb occultations, for which
NO2 is not photolyzed. The dispersion of the GOMOS data
is wider than that of the ACE-FTS data due to the variable
precision for different stars, to the variable local solar time
and also to the much smaller signal-to-noise ratio obtained
by the stellar occultation method.
In the middle panel of Fig. 18, we present the same com-
parison data set corrected for the diurnal variation with the
box model described in Sect. 4.2. Clearly, much better agree-ment is observed and both weighted medians are within the
dispersion of the other instrument. It is interesting that both
experiments (mainly seen in the ACE-FTS profile) report
a decreased negative slope of NO2 in their median profiles
above 40 km. Large NO2 enhancements in the polar winter
mesosphere have previously been reported by several authors
and have been attributed to NO production by solar proton or
by energetic electron precipitation (e.g. Hauchecorne et al.,
2007; Randall et al., 2005a, and references therein). Strong
descent of air occurring in the polar regions, can transport
large quantities of NO from the upper mesosphere-lower
thermosphere to the lower mesosphere or upper stratosphere,thus increasing NO2 concentrations.
In the right panel of Fig. 18, we show the weighted median
difference profile between ACE-FTS and GOMOS. These
are given relative to the GOMOS data set (unlike all the other
satellite comparisons shown in this paper). It can be seen that
between 23 and 43 km there is an agreement to within 10%,
being positive between 37 and 42 km, and above 49 km. The
generally negative bias of ACE-FTS increases to approxi-
mately 55% at 47 km and to more than 100% below 18 km.
It is important to realize that even if the photodiurnal cor-
rection is essential to compare a stellar and a solar occultationinstrument, it is of limited accuracy. Indeed, it is clear that
the true local solar occultation time is crucial to compute the
correction factor (see Fig. 6). This may be quite sensitive to
the geometry of the occultation through the altitude depen-
dence and even with respect to atmospheric refraction. Also,
the GOMOS line-of-sight direction should be taken into ac-
count as well as the extended Sun angular diameter in the
ACE-FTS retrievals. The diurnal effect should be evident
in the GOMOS-ACE comparisons but may be swamped by
other, larger systematic errors.
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T. Kerzenmacher et al.: Validation of NO2 and NO from ACE 5819
5.1.4 MIPAS ESA NO2
For MIPAS, correlative data were only available for a two-
month period in early 2004 for northern mid- and high
latitudes, and the coincidence criteria were chosen to be
300 km and 6 h to have a sufficient number of coincidencesfor the statistics of the comparison. MIPAS ESA data
v4.62 are compared in the period from 21 February 2004 to
26 March 2004. During the first five months of the ACE
mission, only sunsets were measured because of problems
with spacecraft pointing at sunrise. Therefore the latitude
coverage for this comparison is limited to between 20◦ N
and 85◦ N. The comparison has been done including all the
matching pairs of measurements available in the overlap
period. Only MIPAS ESA profiles associated with a success-
ful pressure/temperature and target species retrievals have
been considered.
Wetzel et al. (2007) studied Arctic daytime sunset profiles(ACE-FTS data version 2.2) around 75◦ N, which were com-
pared to MIPAS ESA daytime observations. There the three-
dimensional chemical transport model KASIMA (Karlsruhe
Simulation model of the Middle Atmosphere; Kouker et al.,
1999) was used to photochemically correct the MIPAS ESA
profiles to the time of the ACE-FTS profiles. They used
co-location criteria of 1 h and 300 km, leading to 12 coin-
cidences. The time period was 4 February to 26 March 2004.
They found an overall good agreement (−5.8%) with a small
negative bias of MIPAS below 32 km reaching 40% at the
lowest altitudes. Note that this comparison time period in-
cluded part of the science commissioning prior to the ACEScience Operations phase that started on 21 February 2004.
In the study presented here, we have 84 coincidences in the
period 21 February to 26 March 2004. Panel (a) in Fig. 19
shows the average profiles of ACE-FTS in red, ACE-FTS
(photochemically corrected to the MIPAS times) in black and
the MIPAS ESA profiles in blue. The absolute differences in
panel (b) have combined error bars (mainly from MIPAS).
It can be seen that the differences are small when the error
bars are taken into account. In panel (c) it can be seen that
there is good agreement to within 20% below 32 km, with
a small negative bias for the ACE-FTS for the photochem-
ically corrected data. Above 32 km, the differences are notsmall anymore: the negative bias increases to 75% at 45 km,
but the error bars also become larger.
There are uncertainties above 35 to 40 km in the compari-
son of ACE-FTS with MIPAS ESA, which might be related
to the fact that the ESA retrieval rejects negative values.
These are particularly important if the retrieved VMRs are
close to the noise error (with high noise errors because of the
low temperatures encountered during the measurements for
the comparisons presented here).
0 2 4 6 8NO2 VMR [ppbv]
10
20
30
40
50
h e i g h t [ k m ]
ACE FTSACE FTS boxMIPAS day
(a)
-4 -2 0 2 4ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
20 40 60 80σ [%]
(d)
79
81848484848484848484848484848484858480807975
# o f c o i n c i d e n c e s
Fig. 19. Same as Fig. 10 but for ACE-FTS and MIPAS ESA. In
addition to the ACE-FTS box model corrected data (ACE-FTS box,
black), the uncorrected data is plotted (ACE-FTS, red). Note: here
the error bars in panel (b) are the combined random errors.
5.1.5 OSIRIS NO2
For OSIRIS, the coincidence criteria used are 500 km and
2 h. Local ACE sunset measurements are compared to
OSIRIS evening observations. Too few coincidences are
found at sunrise/morning to make a relevant statistical anal-
ysis. Only profiles that are both inside or both outside the
polar vortex are used. This is done by studying potential
vorticity fields from the European Centre for Medium-range
Weather Forecast (ECMWF). The conversion of OSIRIS
data from number density to VMR is done using ECMWF
temperature and pressure at OSIRIS measurement locations.
Only OSIRIS data with measurement response above 0.5 areused. OSIRIS profiles are interpolated onto the ACE-FTS
and MAESTRO altitude grids. ACE data with reported er-
rors above 100% are rejected. OSIRIS data flagged for bad
pointing are removed. OSIRIS profiles are scaled to the solar
zenith angle of ACE (i.e. 90◦) using box model data for local
OSIRIS conditions. Only profiles for which the magnitude
of the scaling is less than 100% are used. In addition to so-
lar occultation diurnal effects, an ACE-OSIRIS comparison
must contend with limb-scatter diurnal effects (McLinden
et al., 2006), although these are generally smaller and vary
depending on OSIRIS viewing geometry. Model calculations
have been performed using the VECTOR radiative transfermodel (McLinden et al., 2002; Haley and Brohede, 2007) to
quantify diurnal effect errors in each coincident OSIRIS and
ACE profile; these were then applied to the individual pro-
files. The largest portion of the correction lies usually in the
ACE data. Retrieval errors due to concentration gradients
along the scattering/absorption paths (due to varying local
times/solar zenith angles) are only important below 25 km,
because usually biases in the near field are compensated for
opposite biases in the far field. This is, however, not the case
below 25 km, where the signal is becoming saturated and
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5820 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
0 2 4 6 8NO2 VMR [ppbv]
10
20
30
40
50
h e i g h t [ k m ]
ACE-FTSOSIRIS
(a)
-4 -2 0 2 4ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
20 40 60 80σ [%]
(d)
000191382415448472496505514523531536541
542543543543543543543543541539530520514508504500477454312170850
# o f c o i n c i d e n c e s
Fig. 20. Same as Fig. 10 but for ACE-FTS and OSIRIS.
0 2 4 6 8NO2 VMR [ppbv]
10
20
30
40
50
h e i g h t [ k m ]
MAESTROOSIRIS
(a)
-4 -2 0 2 4ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
20 40 60 80σ [%]
(d)
058222222365365431431473473494494512512522522524524524524524524524521521501501488488480480
433433162162000000
# o f c o i n c i d e n c e s
Fig. 21. Same as Fig. 10 but for MAESTRO and OSIRIS.
is henceforth weighted toward the near side. After apply-
ing all this filtering, 543 sunset coincidences remained for
ACE-FTS and 524 sunset coincidences remained for MAE-
STRO. Most coincidences occur in February and March 2004
to 2006 between 30◦ N and 90◦ N. The few results from other
latitudes and seasons are not very different. The results from
ACE-FTS and MAESTRO comparisons are generally simi-
lar.
Figure 20 shows the ACE-FTS–OSIRIS comparison and
Fig. 21 the MAESTRO–OSIRIS comparison. OSIRIS
VMRs are higher at the NO2 peak by about 0.9 ppbv or17% for ACE-FTS and by about 0.7 ppbv or 14% for MAE-
STRO. The results for MAESTRO and ACE-FTS are similar
here due to sampling biases in the OSIRIS comparisons due
to Odin/OSIRIS viewing constraints. Below the peak, the
agreement is very good down to 15 km where there appear
to be issues with the MAESTRO data. The good agreement
below 25 km (especially for ACE-FTS) indicates that the di-
urnal effect correction is working appropriately.
The random difference (1σ ) is around 20% just below
the peak and increases towards lower and higher altitudes
(Fig. 21c). The random differences are larger for MAESTRO
comparisons at the upper edge of the altitude range.
5.1.6 SCIAMACHY NO2 total columns from nadir mea-
surements
For the nadir comparisons, all SCIAMACHY measurements
within 200 km of the ACE occultation measurements taken
on the same day were averaged into one value for the com-
parisons. This leads to about 8000 coincidences. Profiles
that did not extend to sufficiently low altitudes and profiles
for which the diurnal correction could not be calculated were
excluded. There were also missing MAESTRO profiles that
could not be taken into account for the comparisons.
To correct for photochemistry, the SCIAMACHY NO2
vertical column is multiplied with photochemical correc-
tion factors derived with the photochemical model described
earlier (see Sect. 4.2), integrated over the stratosphere andinterpolated linearly on the times of the overpass. Then
these diurnally scaled SCIAMACHY vertical column den-
sities were compared to the corrected ACE-FTS and MAE-
STRO partial columns. Figure 22 shows the comparisons of
ACE-FTS and MAESTRO NO2 partial columns and SCIA-
MACHY NO2 total columns. They show very good corre-
lations, r=0.94 and 0.91, respectively, with both ACE par-
tial columns are in general smaller than the SCIAMACHY
total columns (as expected). The diurnal effect was quanti-
fied by forward modelling the expected error for each ACE-
SCIAMACHY coincidence and then applied as a correction
to the partial column of the ACE instruments. Typically thediurnal effect led to an overestimate in the ACE partial col-
umn by about 12%.
As mentioned above, it is expected that SCIAMACHY to-
tal columns are larger than ACE partial columns. The dif-
ferences seen are of the order of the expected tropospheric
contribution of about 0.5×1015 molec/cm2 with some scat-
ter introduced either by polluted scenes, which have not
been removed fully, or the photochemical correction, which
is expected to introduce a significant uncertainty when the
time difference is large. Interestingly, the correlation be-
tween SCIAMACHY columns and ACE-FTS columns is
more compact although the measurement principle (UV-VISabsorption spectroscopy) is very similar to the one used by
MAESTRO. The main conclusion from this comparison is
that the overall consistency of the two ACE NO2 products
with SCIAMACHY nadir columns is very high with no in-
dication of systematic latitudinal/SZA biases larger than the
intrinsic uncertainties of the comparison (based on further
examination of the data, not shown). The photochemical
correction on the SCIAMACHY data, however, is relatively
large in many cases and introduces a significant uncertainty
in the comparison.
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T. Kerzenmacher et al.: Validation of NO2 and NO from ACE 5821
0 2 4 6 8 10
SCIAMACHY NO2 total column [1015
cm-2
]
0
2
4
6
8
10
A C E - F T S N O 2 p a r t i a l c o l u m n [ 1 0 1 5 c
m - 2 ]
ACE-FTS = 0.77 SCIAMACHY + 0.18
r = 0.94
0 2 4 6 8 10
SCIAMACHY NO2 total column [1015
cm-2
]
0
2
4
6
8
10
M A E S T R O N O 2 p a r t i a l c o l u m n [ 1 0 1 5 c
m - 2 ]
MAESTRO = 0.79 SCIAMACHY + 0.38
r = 0.91
Fig. 22. Scatter plot of the ACE-FTS (left) and the MAESTRO (right) NO 2 partial columns (calculated between 14.5 to 46.5 km) and the
SCIAMACHY NO2 nadir total columns. In both figures the red lines are the least-squares linear fit to the data, with the slope, intercept, and
correlation coefficient given in the figures. The dashed black lines show the one-to-one line relationship for comparison.
5.2 Comparisons with balloon measurements
5.2.1 SPIRALE NO2 measurements near Kiruna
The SPIRALE NO2 measurement was made on 20 Jan-
uary 2006 between 17:46 UT and 19:47 UT, with a
vertical profile obtained during ascent between 17.0 and
27.2 km. The measurement position remained rather con-
stant, with the balloon mean location of 67.6±0.2◦ N and
21.55±0.20◦ E. The comparison is made with ACE occul-
tation sr13151, which occurred 13 h later (on 21 Jan-
uary 2006 at 08:00 UT) and was located at 64.28◦ N,21.56◦ E, i.e. 413 km away from the SPIRALE position.
Using the MIMOSA (Modele Isentropique de transport
Mesoechelle de l’Ozone Stratospherique par Advection) con-
tour advection model (Hauchecorne et al., 2002), potential
vorticity maps in the region of both measurements have been
calculated each hour between 17:00 UT on 20 January and
08:00 UT on 21 January on isentropic surfaces, every 50 K
from 400 K to 800 K (corresponding to 16 to 30 km height).
From these potential vorticity fields, it can be deduced that
the SPIRALE and ACE profiles were located in similar air
masses in the well-established polar vortex for the whole
range of altitudes sounded by SPIRALE. The dynamicalsituation was very stable with potential vorticity agreement
better than 10%, which gives a geophysical situation suitable
for direct comparisons.
Since SPIRALE measurements were performed at night
(when the NO2 VMR is a maximum) and ACE measure-
ments were performed at twilight (when there is a strong de-
crease of NO2), the diurnal variations of NO2 had to be taken
into account. Appropriate coefficients deduced from the pho-
tochemical model described in Sect. 4.2 have been applied to
the ACE NO2 measurements.
0.0 0.5 1.0 1.5 2.0NO2 VMR [ppbv]
16
18
20
22
24
26
h e i g h t [ k m ]
(a)
ACE FTSMAESTROSPIRALE rawSPIRALE smooth
-0.5 0.0 0.5ACE-val [ppbv]
(b)
-100 0 100(FTS-val)/mean [%]
-100 0 100(ACE-val)/mean [%]
(c)
Fig. 23. (a) NO2 profiles obtained by SPIRALE on 20 January 2006
(in turquoise (raw) and blue (smoothed)), sunrise occultation 13151
on 21 January 2006: ACE-FTS (in red) and MAESTRO (in black),
ACE corrected by using a photochemical model (dashed lines). (b)
Absolute differences between the ACE instruments and SPIRALE
(smooth) and the photochemically corrected profiles (dashed). (c)
Relative differences between SPIRALE data and ACE uncorrected
(solid) and corrected data (dashed). The region ±20% is highlighted
in yellow. Error bars represent the combined random error for pan-
els (b) and (c).
In Fig. 23, between 17 and 23.6 km height, SPIRALE
measurements show the expected denoxification (removal of
NOx) with NO2 concentrations close to zero (accounting for
error bars) in agreement with a vertical profile (not shown)
simulated by the REPROBUS (REactive Processes Ruling
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5822 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
0 1 2 3 4NO2 VMR [ppbv]
10
15
20
25
30
h e i g h t
[ k m ]
(a)
ACE-FTSMAESTROSAOZ
-0.5 0.0 0.5ACE-val [ppbv]
(b)
-50 0 50(FTS-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
Fig. 24. (a) NO2 profiles obtained by SAOZ at Aire-sur-l’Adour
on 7 May 2005 (blue), sunrise occultation 9317 on 6 May 2005:
ACE-FTS (red) and MAESTRO (black). (b) Absolute differencesbetween SAOZ and the ACE instruments. (c) Relative differences
between SAOZ and the ACE instruments. The region ±20% is high-
lighted in yellow. Error bars represent the combined random error
for panels (b) and (c).
0 1 2 3 4NO2 VMR [ppbv]
10
15
20
25
30
h e i g h t [ k
m ]
(a)
ACE-FTSMAESTROSAOZ
-0.5 0.0 0.5ACE-val [ppbv]
(b)
-50 0 50(FTS-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
Fig. 25. (a) NO2 profiles obtained by SAOZ at Niamey, Niger on7 (dotted blue), 10 (solid blue) and 19 August 2006 (dashed blue);
ACE occultation sunset 16076 on 7 August 2006, ACE-FTS in red
and MAESTRO in black. (b) Absolute differences between SAOZ
and the ACE instruments. (c) Relative differences between SAOZ
and the ACE instruments. The region ±20% is highlighted in yel-
low. Error bars represent the combined random error for panels (b)
and (c).
the Ozone BUdget in the Stratosphere) Chemical Transport
Model (CTM) (Lef evre et al., 1998) for these polar winter
conditions. This result clearly differs from the ACE-FTS
and MAESTRO observations (with or without photochem-
ical corrections), which show significant amounts of strato-
spheric NO2 in the lower stratosphere. Such NO2 enhance-
ments are also present in the vertical profiles previously ob-
tained at polar latitudes by balloon-borne instruments using
remote-sensing techniques (e.g. Payan et al., 1999; Riviere
et al., 2002) in contradiction with our current knowledge of polar chemistry. As demonstrated by Berthet et al. (2007),
such non-zero values can be attributed to effects of NO2
local inhomogeneities present at higher altitudes along the
lines-of-sight of these instruments and mainly resulting from
perturbed dynamical situations. In such cases, the validity
of the spatial homogeneity hypothesis inherent in remote-
sensing methods can be ruled out, consequently affecting
the retrievals of the lower part of the vertical profile. In
the ACE observation case, the vortex appears to be vertically
distorted, as shown by the MIMOSA potential vorticity fields
between 800 and 950 K, which are above the vertical lev-
els corresponding to the SPIRALE measurements. Some of the ACE lines-of-sight appear to cross the vortex edge, thus
sounding both denoxified air masses in the inner part of the
vortex (as shown by SPIRALE inside the vortex) and NO2-
richer air in the outer part of the vortex. Above 23.6 km,
NO2 concentrations measured by SPIRALE sharply increase
and the disagreement between both instruments is reduced to
less than 50%. Note that the REPROBUS CTM simulates a
profile with a similar gradient above 23.6 km (Berthet et al.,
2007).
5.2.2 SAOZ balloon measurements of NO2 from Aire-sur-
l’Adour and Niamey
The SAOZ balloon profiles available for comparison with
ACE-FTS and MAESTRO are those from one flight from
Aire-sur-l’Adour in France (43.7◦ N, 0.2◦ W) and three from
Niamey, Niger (13.4◦ N, 2.1◦ E). Two profiles are available
for each flight: during the ascent of the balloon in the late
afternoon and during sunset occultation from float altitude.
The latter is more precise so it is used in the comparisons.
Figure 24 shows the comparisons for the flight from Aire-
sur-l’Adour launched on 7 May 2005 at 18:00 UT. There is
a coincident ACE sunrise (sr 9317) profile on 6 May 2005 at
05:00 UT, which is at a distance of about 700 km and 37 h
earlier. It can be seen that despite of the large time differencethere is very good agreement between all three instruments.
In this case, MAESTRO agrees better than ACE-FTS (gen-
erally to within 20%), whereas ACE-FTS shows a low bias
from 57% at 14.5 km to 8% at 22.5 km. There is no differ-
ence between the SAOZ float occultation measurements and
the ascent profiles (not shown).
The closest flight in the tropics took place at Niamey,
Niger on 7 August 2006 at 18:00 UT, for which there was
a sunset occultation (ss16076) at 18:51 UT, at a distance of
about 850 km. However, because of the 22 km float altitude
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0 1 2 3 4 5FTIR NO2 partial column [1015 cm−2]
0
1
2
3
4
5
A C E − F T S N O 2 p a
r t i a l c o l u m n [ 1 0 1 5 c
m − 2 ]
Ny ÅlesundKirunaBremenTorontoIzanaWollongong
ACE−FTS = 0.95 FTIR + 0.21r = 0.91
0 1 2 3 4 5FTIR NO2 partial column [1015 cm−2]
0
1
2
3
4
5
M A E S T R O N O 2 p a r t i a l c o l u m n [ 1 0 1 5 c
m − 2 ]
Ny ÅlesundKirunaBremenTorontoIzanaWollongong
MAESTRO = 1.02 FTIR + 0.21r = 0.89
Fig. 26. Scatter plots of the ACE-FTS (left) and the MAESTRO (right) and ground-based FTIR NO 2 partial columns. For both panels the
red lines are the linear least-squares fit to the data, with the slope, intercept, and correlation coefficient given in the figures. The black lines
show the one-to-one linear relationship for comparison.
of this flight, which was dedicated to the study of NOx pro-duction by lightning near a thunderstorm, the profiles only
extend from 16 to 21 km. Because the measurements are very
consistent within this altitude range with those of two other
flights performed on 10 and 19 August up to 28 km and be-
cause NO2 is not expected to vary in the stratosphere in the
tropics, the data from the two later flights were also used in
the comparison although not co-located with ACE. Figure 25
shows the profiles of the three flights together with those of
ACE-FTS and MAESTRO. It can be seen that the variability
of the SAOZ NO2 is indeed very small: sunset NO2 pro-
files are very close together. They compare very well with
the profiles from the ACE instruments. The agreement with
ACE-FTS is better than 20% above 16 km with a slight neg-ative bias. The MAESTRO NO2 VMR is larger than both
the SAOZ and ACE-FTS VMRs between ∼18.5 and 25 km,
and agrees with the three SAOZ profiles to within 20% above
22 km. Below 17 km the data are less reliable, because of the
large variation of NO2 in the upper troposphere and the trop-
ical tropopause layer caused by lightning.
5.3 Ground-based FTIR NO2
For the validation of ACE NO2 by ground-based FTIRs, data
are available from six stations: Ny Alesund, Kiruna, Bremen,
Toronto, Izana and Wollongong (see Table 1). For each sta-tion, the ACE-FTS profiles were interpolated onto the FTIR
retrieval grid and extended below the lowest retrieved alti-
tude using the FTIR a priori VMR values. This combined
profile was smoothed using the FTIR averaging kernels and
a priori profile, as described in Sect. 4.1, to minimize the
smoothing error (Rodgers and Connor, 2003). For the calcu-
lation of partial columns, atmospheric densities were needed;
the density derived from the pressure and temperature pro-
files used in the FTIR retrievals was used for both the ground-
based and the ACE measurements. The lower limit of the al-
titude range of the partial columns at each station was deter-mined by the ACE-FTS altitudes and the upper limit was de-
termined by the sensitivity of the FTIR measurements, which
was required to be 0.5 or greater. The sensitivity of the FTIR
measurements was calculated using the sum of the elements
of the columns of the averaging kernel matrix that was not
normalized with the a priori profile. This results in a sensi-
tivity with respect to altitude (Vigouroux et al., 2007). This
sensitivity indicates the contribution to the retrieval from the
measurement. Thus a sensitivity greater than 0.5 means that
at that altitude more than half of the information is being
gained from the measurement itself and less than half re-
mains from the a priori VMR profile.
Table 3 lists the microwindows used at the participatingsites, and the altitude ranges where the sensitivity for the
FTIR measurements were greater than 0.5 and for which
ACE data were available. The partial columns for NO2 at
the different locations were calculated for these altitude
ranges. As can be seen, the altitude ranges over which the
partial columns were calculated vary from station to station.
For Kiruna and Izana, the profiles were scaled a priori pro-
files and therefore there were no averaging kernels for NO 2
and DOFS were not calculated. Averaging kernel smoothing
could not be applied for these two stations. Therefore partial
columns of unsmoothed ACE profiles were compared with
partial columns from Kiruna and Izana. The DOFS for theother stations are indicated in Table 3. It can be seen that the
Bremen result has 0.1 DOFS, because the altitude range with
sensitivity >0.5 is very small (from 19.6 to 24.4 km). The
Wollongong result has 0.6 DOFS, which is due to large wa-
ter vapour concentration in the atmosphere and therefore low
signal-to-noise ratio. The ACE data were adjusted to match
the local times of the FTIR stations using the photochemical
box model (see Sect. 4.2).
In Table 3, it can be seen that the agreement between
the ground-based stations and the ACE instruments is good:
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5824 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
Table 3. Results of the NO2 partial column comparisons of ACE-FTS and MAESTRO with the ground-based FTIRs. The microwindow(s)
used in the retrievals are listed in column 2. For each ACE / FTIR pair, the number of coincidences, the vertical range used to calculate the
partial columns and the corresponding degrees of freedom for signal (DOFS) are given in columns 3 to 5. The mean difference and 1σ
standard deviation of the mean are indicated in columns 6 and 7 for ACE-FTS and MAESTRO, respectively. The retrieval code (with version
number) and the spectroscopic database used by the FTIRs are given in the footnotes.
FTIR Microwindow(s)b,c # of Range DOFS Mean diff. ± std dev. [%]
stationa [cm−1] pairs [km] ACE-FTS MAESTRO
Ny Alesund 2914.5900–2914.7070 45 14.8–39.2 1.0 +20.5±25.4 +25.6±29.1
Kirunad 2888.2500–2888.3200 21 19.5–34.2 – +11.1±20.6 +22.0±26.1
2893.2806–2893.3610
2911.6610–2911.7194
2914.6000–2914.7000
Bremen 2914.5900–2914.7070 72 19.6–24.4 0.1 +2.8± 7.5 +5.4± 8.2
Toronto 2914.5900–2914.7070 20 15.6–39.6 2.1 +1.1±17.4 +5.0±20.4
Izanad 2888.2500–2888.3200 10 19.5–52.8 – −9.3±15.1 +1.4±18.5
2893.2806–2893.3610
2911.6610–2911.7194
2914.6000–2914.7000
Wollongong 2914.5500–2914.8000 13 23.0–37.0 0.6 −6.3±14.2 +12.0±13.2
Total 181 +7.3±19.6 +12.8±22.1
a Retrieval codes: PROFFIT92 is used for Kiruna and Izana with the solar model of Hase et al. (2006).
SFIT2 is used for Ny Alesund (v3.92a), Bremen (v3.92a), Toronto (v3.82β3) and Wollongong (v3.92).b Spectroscopic linelist: HITRAN1996 for Kiruna and Izana. All other stations use HITRAN 2004.c Multiple microwindows are fitted simultaneously during the retrieval process for some stations.d Izana and Kiruna profiles are scaled, i.e. no DOFS were calculated.
within approximately 20% for all but a few cases, and gen-
erally better than this. For ACE-FTS, the mean differences
lie between 20.5% with σ =25.4% for Ny Alesund and −9.3%
with σ =15.1% for Izana. The MAESTRO differences are be-
tween 25.6% with σ =29.1% for Ny Alesund and 1.4% withσ =18.5% for Izana. The mean relative difference is posi-
tive in the MAESTRO comparisons, and positive for all but
two stations in the ACE-FTS comparisons. This suggests
that the ACE-FTS and MAESTRO partial columns have a
small positive bias. Good correlation between ACE and the
FTIR partial columns is seen in the scatter plots of the data
from all stations. Figure 26 shows a tight correlation, with a
correlation coefficient, r, defined as
r = covariance of ACE and VAL
σ ACEσ VAL(5)
where σ ACE = standard deviation of ACE and σ VAL = stan-dard deviation of VAL. The correlation, r , is 0.91 for ACE-
FTS and 0.89 for MAESTRO. The line fitted to the ACE-FTS
versus FTIR data has slope 0.95, indicating good agreement,
and intercept 0.21×1015 molec/cm2 and that for MAESTRO
versus FTIR, slope 1.02 and intercept 0.21×1015 molec/cm2.
The largest standard deviations in Table 3 are found for
the high-latitude stations. For Kiruna, 8 out of 12 days of
available measurements are during the strong vortex winter
of 2005, but these data do not show more scatter than
Ny Alesund, which has only two available measurement days
during the same period. There also do not appear to be sig-
nificant gradients in NO and NO2 across the vortex edge for
the corresponding ACE-FTS measurements. Therefore we
do not think that the larger scatter at the northern high lati-
tude stations is due to the polar vortex.
5.4 Ground-based UV-VIS NO2
For the ground-based UV-VIS comparisons, we have data
from Harestua, Norway (60.2◦ N, 12.8◦ E) and Vanscoy,
Canada (52.02◦ N, 107.03◦ W) for profiles and column com-
parisons.
5.4.1 Ground-based NO2 profiles and partial columns at
Harestua
Both ACE-FTS and MAESTRO NO2 profiles have been
compared to height-resolved data retrieved from ground-based zenith-sky UV-VIS observations. For the compari-
son at Harestua, the maximum distance between the sta-
tion and the ACE NO2 measurements was 750 km. The
measurements by ACE and the ground-based observations
were required to be on the same day. Ground-based pro-
files are converted to the solar zenith angle corresponding to
the ACE-FTS and MAESTRO NO2 measurements using the
stacked box photochemical model PSCBOX (Hendrick et al.,
2004) included in the profiling algorithm. Photochemical
conditions are therefore similar for both ACE and ground-
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Table 4. Same as Table 3, but for the NO partial column comparisons between ACE-FTS and the ground-based FTIRs.
FTIR Microwindow(s)b,c # of Range DOFS Mean diff.
stationa [cm−1] pairs [km] ± std dev. [%]
Ny Alesund 1899.8017–1900.1981 50 24.4–41.3 0.9 −67.5±17.4
Kiruna 1900.0278–1900.1220 18 19.5–44.8 1.6 −39.7±15.4
1929.0100–1929.0400Toronto 1899.8800–1900.1500 11 25.1–47.9 1.0 −25.7±32.0
Izana 1900.0278–1900.1220 9 22.1–44.8 1.3 −20.6±31.8
1929.0100–1929.0400
Wollongong 1900.0000–1900.1000 19 23.0–43.0 0.7 −14.5±16.1
1900.4900–1900.5400
1903.0500–1903.2000
1928.5400–1928.7000
Total 107 −46.7±29.6
a Retrieval codes: PROFFIT92 is used for Kiruna and Izana with the solar model
of Hase et al. (2006). SFIT2 is used for Ny Alesund (v3.92a), Toronto (v3.82β3)
and Wollongong (v3.92).b Spectroscopic linelist: HITRAN2001 for Kiruna and Izana. All other stations
use HITRAN 2004.c Multiple microwindows are fitted simultaneously during the retrieval process
for some stations.
based UV-VIS profiles. The ACE data from both ACE-
FTS and MAESTRO were smoothed with the averaging ker-
nels from the ground-based instrument. After applying these
criteria, the following numbers of coincident events have
been selected for comparison for the 2004 to 2005 period:
13sunrises (May and September) and 15 sunsets (March and
July) for ACE-FTS and six sunrises (September) and 11 sun-
sets (March and July) for MAESTRO.Figure 27 shows the comparison results for all the sun-
rise profiles and Fig. 28 for the sunset profiles. Below 32 to
35 km, ACE-FTS reports more NO2 than the ground-based
instrument with a maximum difference of 23% at 23 km for
sunrise and 25% at 25 km for sunset. Qualitatively, simi-
lar results are obtained with MAESTRO. However, the pos-
itive bias with MAESTRO is larger than for ACE-FTS with
a maximum value of about 33% at about 22 km. At sun-
rise, the observed differences are just outside the variability
of both ground-based and MAESTRO profiles.
In order to minimize the effect of the vertical smooth-ing associated with the ground-based measurements on the
comparison (Hendrick et al., 2004, 2007), NO2 partial
columns from 17 to 35 km are also compared. This roughly
corresponds to the common altitude range where ACE-FTS,
MAESTRO, and the ground-based UV-VIS measurements
are significantly sensitive to the vertical distribution of NO 2.
Partial column comparison results are presented in Fig. 29.
The ACE-FTS results are higher than the UV-VIS results
by 15% at sunrise and 14% at sunset. This corresponds to
absolute difference values of 0.4 and 0.5×1015 molec/cm2,
0 2 4 6 8 10NO2 VMR [ppbv]
10
20
30
40
50
h e i g h t [ k m ]
(a)ACE-FTSMAESTRODOAS (F)DOAS (M)
-1 0 1ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
10 20 30 40σ [%]
(d)
Fig. 27. (a) Mean smoothed ACE-FTS (red stars), MAESTRO
(black circles) and ground-based UV-VIS NO2 sunrise profiles at
Harestua for 2004 to 2005: filled blue diamonds indicate the mean
UV-VIS profile for the comparison with ACE-FTS (DOAS (F)),
open purple diamonds indicate the mean UV-VIS profile for the
MAESTRO comparison (DOAS (M)). (b) Absolute differences. (c)Relative differences. The ±20% region is highlighted in yellow. (d)
Standard deviations of the distributions, 1σ , relative to the mean
NO2 VMR at each altitude, for all coincident events, for ACE-FTS
(red), MAESTRO (black) and UV-VIS (blue and purple). The num-
ber of coincidences is 13 (11 at 15 km) for ACE-FTS and 6 for
MAESTRO at all levels. The error bars represent the uncertainty
in the mean.
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5826 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
0 2 4 6 8 10NO2 VMR [ppbv]
10
20
30
40
50
h e i g h t [ k m ]
(a)ACE-FTSMAESTRODOAS (F)DOAS (M)
-1 0 1ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
10 20 30 40σ [%]
(d)
Fig. 28. Same as Fig. 27 but for sunset profiles. The number of co-
incidences is 15 (12 at 15 km) for ACE-FTS and 11 for MAESTRO
at all levels.
0
2
4
6
N O 2 p a r t i a l c o l u m n
[ 1 0 1 5 c
m - 2 ]
ACE-FTSMAESTRODOAS
Jul2004 Jan2005 Jul2005
-50
0
50
d i f f e r e n c e s [ % ]
Mar2004 May2004 Jul2004 Sep2004 Nov2004 Jan2005 Mar2005 May2005 Jul2005 Sep2005
-50
0
50
d i f f e r e n c e s [ % ]
Fig. 29. Comparison of NO2 partial columns from 17 to 35 km
from ACE-FTS (red stars), MAESTRO (black triangles) and the
ground-based UV-VIS (blue diamonds) at Harestua for 2004 and
2005. Sunrises are indicated with open and sunsets with filled sym-
bols. The relative differences with respect to the mean appear in
the lower panel. The ±20% region is indicated in yellow. The error
bars on the ground-based UV-VIS columns are estimated from the
total retrieval errors on the retrieved ground-based profiles (Hen-
drick et al., 2004, 2007).
respectively. However, these differences are not significant
since ACE-FTS partial columns are always within the error
bars associated with the ground-based partial columns. As
expected from the profile comparison, a larger difference is
obtained with MAESTRO: 30% on average at sunrise and
26% at sunset, which corresponds to absolute difference val-
ues of 0.7 and 0.8×1015 molec/cm2, respectively. For some
of the coincident events, these differences are significant
since the MAESTRO partial column values are outside the
0 2 4 6 8NO2 VMR [ppbv]
10
20
30
40
50
h e i g h t [ k m ]
(a)
ACE-FTSMAESTROSAOZ
-1 0 1ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
5 10 15 20σ [%]
(d)
Fig. 30. (a) Mean ACE-FTS (red stars), MAESTRO (black cir-
cles) and ground-based UV-VIS NO2 profiles (blue diamonds) at
Vanscoy for September 2004. (b) Absolute differences and (c) rel-
ative differences are shown. (d) Standard deviations of the distribu-
tions, 1σ , relative to the mean NO2 VMR at each altitude, for all
coincident events, for ACE-FTS (red), MAESTRO (black) and UV-VIS (blue). The ±20% region is indicated in yellow. The number of
coincidences is 5 for all levels.
0
1
2
3
4
5
N O 2 p a r t i a l c o l u m n
[ 1 0 1 5 c
m - 2 ]
ACE-FTSMAESTROSAOZ
01 Sep2004
02 Sep2004
03 Sep2004
04 Sep2004
05 Sep2004
06 Sep2004
07 Sep2004
-50
0
50
d i f f e r e n c e
s [ % ]
01 Sep2004
02 Sep2004
03 Sep2004
04 Sep2004
05 Sep2004
06 Sep2004
07 Sep2004
-50
0
50
d i f f e r e n c e
s [ % ]
Fig. 31. Comparison of NO2 partial columns (between 10 and
45 km calculated from the ACE-FTS (red stars), MAESTRO (black
triangles), and ground-based UV-VIS (blue diamonds) NO2 profiles
at Vanscoy for 1 to 6 September 2004. The relative differences ap-
pear in the lower panel. The ±20% region is highlighted in yellow.
The error bars on the ground-based UV-VIS columns are estimatedfrom the total retrieval errors on the retrieved ground-based profiles
(Hendrick et al., 2004, 2007).
error bars associated with the ground-based columns. Be-
cause the ACE data set does not report systematic errors, a
combined error bar could not be calculated, however we ex-
pect the differences to be within the combined error bars. The
partial column comparison results from the DOAS system at
Harestua (60.2◦ N), (14 to 15% for ACE-FTS and 26 to 30%
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T. Kerzenmacher et al.: Validation of NO2 and NO from ACE 5827
for MAESTRO), show similar magnitudes to those from the
FTIR measurements at Kiruna (67.8◦ N), (11% for ACE-FTS
and 22% for MAESTRO for the smaller columns).
5.4.2 Ground-based MANTRA SAOZ NO2 profiles and
partial columns at Vanscoy
For the SAOZ profile comparisons, the method described forHarestua in Sect. 5.4.1 has been applied, but sunrises and
sunsets have not been distinguished, because only five co-
incidences were available. In order to convert the SAOZ
profiles into VMRs, pressure and temperature profiles from
ACE-FTS were used. The profiles from the ACE instruments
were smoothed with the SAOZ averaging kernels. No diurnal
scaling needed to be applied because the measurement took
place at the same solar zenith angles. It can be seen in Fig. 30
that the profiles agree very well, for ACE-FTS typically,
i.e. on average, to within 15% (maximum +35%), and for
MAESTRO typically to within 10% (maximum +25%) from
12 to 43 km as shown in Table 5. The partial columns cal-
culated from 10 to 45 km also show a very good agreement
(within retrieval errors): only one MAESTRO partial column
that is not within 20% of the SAOZ partial column (Fig. 31).
This result was anticipated because the measurements
were calculated during the MANTRA campaign, which took
place at midlatitudes in late summer, a time of minimal dy-
namical variability, i.e. ideal conditions for validation studies
(Wunch et al., 2005).
6 Results for the NO and NOx comparisons
In this section, the comparisons available for NO will beshown. Data from only two satellite instruments were avail-
able for comparison: HALOE and MIPAS IMK-IAA. The
MIPAS comparisons were done for NOx rather than NO
or NO2 because of the difficulty of correcting for diurnal
variations under perturbed (NOx descent) conditions. The
only other datasets available for NO comparisons are the
ground-based FTIR measurements from the NDACC sites
Ny Alesund, Kiruna, Toronto, Izana and Wollongong.
6.1 MIPAS IMK-IAA comparison of NO and NOx
The observational period under investigation includes the ex-
traordinary 2004 Arctic winter, which was characterized byenormous amounts of NOx transported downwards from the
upper atmosphere inside the polar vortex (e.g. Lopez-Puertas
et al., 2005; Randall et al., 2005a) raising stratospheric NOx
abundances by more than 1 ppm in February/March. These
unusual atmospheric conditions make it difficult to combine
this comparison with the others undertaken during this vali-
dation exercise. For the comparison, we used as coincidence
criteria a maximum time difference of 18 h and a maximum
spatial mismatch of 1000 km with a maximum potential vor-
ticity difference of 30%. MIPAS version 9.0 NO2 observa-
Fig. 32. Longitudinal distributions of ACE-FTS and MIPAS IMK-
IAA NOx abundances measured on 18 March 2004 at VMR peak
height (top) and respective geographic locations of the measure-
ments (bottom). The error bars indicate random errors. Black di-
amonds: ACE-FTS, open squares: MIPAS (color coding: yellow,
orange, red: daytime measurements; green, blue: nighttime mea-surements).
0 100 200 300VMR [ppbv]
10
20
30
40
50
60
70
h e i g h t [ k m ]
ACE-FTSMIPAS
(a)
-100 0 100ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
50 100 150 200σ [%]
(d)
000198290386
450489493487477489490493452414448431410433445458422410434429419317284225
# o f c o i n c i d e n c e s
Fig. 33. Same as Fig. 10, for MIPAS IMK-IAA NO2 night and
ACE-FTS NOx (February–March 2004, all days merged). Coinci-
dence criteria: distance 1000 km, time 18 h, potential vorticity dif-
ference 30%, MIPAS solar zenith angle >96◦.
tions close to high-latitude (75 to 80◦ N) ACE occultations
are available for 22, 28 February and 4, 12 March 2004. Fur-thermore, on 18 and 25 March, MIPAS observations of both
NOx species could be compared to ACE-FTS measurements
taken around 69◦ N and 56◦ N, respectively. Since a chemi-
cal transport model that could properly account for NOx de-
scent during polar winter was not available, a photochemi-
cal correction to account for the diurnal cycling of the NOx
species could not be applied here. Thus, only MIPAS night-
time NO2 measurements were compared to ACE-FTS NOx
(the sum of the NO2 and NO products) for observations until
12 March 2004, assuming that NOx is in the form of NO2 at
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0 2 4 6 8 10 1214NO VMR [ppbv]
10
20
30
40
50
60
70
h e i g h t [ k m ]
ACE-FTSHALOE(a)
-1 0 1ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
20 40 60 80σ [%]
(d)
16343636363636
36363636363636363636363635331710513
# o f c o i n c i d e n c e s
Fig. 36. Same as Fig. 10 but for HALOE NO.
6.2 HALOE NO
For NO, the HALOE and ACE-FTS data sets were searched
for coincident measurements, defined as occurring within 2 h
and 500 km. A total of 36 coincidences were found; five of
these corresponded to satellite sunrise occultations in both
instruments, while the other 31 corresponded to satellite sun-
set occultations in both instruments. The sunset coincidences
occurred from 4 to 10 July 2004 (29 coincidences, average
latitude 66◦ N) and 15 August 2005 (two coincidences, av-
erage latitude 49◦ S); the sunrise coincidences occurred on
6 and 7 September 2004 (five coincidences, average latitude
60◦ N). Thus the majority of the comparisons correspond to
polar summer conditions in the Northern Hemisphere. Be-
cause only five coincidences corresponded to satellite sunriseoccultations, the results below do not distinguish between
sunrise-sunrise and sunset-sunset comparisons; thus no in-
formation is gained regarding possible sunrise/sunset biases
in the ACE-FTS measurements.
Figures 36 and 37 show the average NO profiles mea-
sured by ACE-FTS and HALOE for all coincidences. Only
measurements where the reported error for ACE-FTS and
HALOE was less than 100% are included in the results pre-
sented. Because VMRs vary strongly over the altitude range
of the retrievals, the profiles are shown on a linear scale
from 20 to 70 km, and on a log scale from 90 to 110 km.
Both instruments show very similar profile shapes, with astratospheric VMR peak near 45 km, and generally increas-
ing VMRs above 65 km. ACE-FTS VMRs are biased slightly
low compared to HALOE below about 48 km, and slightly
high from 50 to 64 km. There are gaps in the curves be-
tween 70 and 90 km (not shown) because there were fewer
than three coincident measurements where both instruments
reported errors less than 100%. In this altitude range, the
NO densities (not shown) are one to two orders of mag-
nitude lower than below 65 km or above 90 km, so the re-
trievals are much more difficult. When both instruments do
102 103 104 105
NO VMR [ppbv]
90
95
100
105
110
h e i g h t [ k m ]
ACE-FTSHALOE
(a)
-10000 0 10000ACE-val [ppbv]
(b)
-50 0 50(ACE-val)/mean [%]
-50 0 50(ACE-val)/mean [%]
(c)
10 100 1000σ [%]
(d)
1013
18
24
32
33
3334
36
35
36
35
35
36
36
34
28
22
15
# o f c o i n c i d e n c e s
Fig. 37. Same as Fig. 36 but for the height range 90 to 108 km
and with logarithmic abscissae for panel (a) and (d). One of the
standard deviation curves in panel (a) is discontinuous because of
the logarithmic axis.
have data, the differences above 65 km are often significantly
larger than at the lower altitudes. Dotted lines in panels (a) of
the figures represent the standard deviations of the distribu-
tion of profiles measured by each instrument. Qualitatively, it
is clear that both instruments measure similar variability be-
low 60 km as seen in Fig. 36d. Above this altitude, profiles
from both instruments show substantially more variability,
but not necessarily of the same magnitude.
Variability is quantified more clearly in panels (d) of
Figs. 36 and 37, which show the standard deviations of the
distributions relative to the mean VMRs, again separately for
the low- and high-altitude cases. Below 65 km, there is very
good agreement between ACE-FTS and HALOE, with bothinstruments showing slightly increasing standard deviations
above about 35 km, and more steeply increasing standard de-
viations below 35 km. The standard deviations shown here
reflect both instrument precision and geophysical variabil-
ity in the measurements. Above 64 km (only shown from
90 km), there is substantial disagreement between the ACE-
FTS and HALOE standard deviations, with ACE-FTS show-
ing higher variability. It is possible that these standard devi-
ation differences are due to different geophysical conditions
sampled by the instruments, but this should not be a large ef-
fect given the relatively tight coincidence criteria employed
here. In addition, geophysical variability would not be ex-pected to result in a bias in one instrument compared to the
other, since it is unlikely that one instrument would always
sample geophysical conditions that were biased in the same
way with respect to the conditions sampled by the other in-
strument. We thus speculate that the precision of the ACE-
FTS measurements is generally worse than that of HALOE
above 64 km.
Panels (c) of Figs. 36 and 37 show the percent differ-
ences between the instruments. As noted above, measure-
ments from ACE-FTS are biased slightly low compared to
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5830 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
0 1 2 3 4 5FTIR NO partial column [1015 cm−2]
0
1
2
3
4
5
A C E − F T S
N O p a r
t i a l c o l u m n [ 1 0 1 5 c m − 2 ] Ny Ålesund
KirunaTorontoIzanaWollongong
ACE−FTS = 0.52 FTIR + 0.31r = 0.59
Fig. 38. Scatter plot of the ACE-FTS and ground-based FTIR NO
partial columns. The red line is the linear least-squares fit to the
data, with the slope, intercept, and correlation coefficient given in
the figure. The black line shows the one-to-one line relationship forcomparison.
HALOE below 48 km, with differences generally within∼10
to 15%. From 49 to 64 km, ACE-FTS measurements are bi-
ased slightly high compared to HALOE, with differences in-
creasing to 21% at 60 km. To summarize, the overall agree-
ment below 60 km is excellent, with differences within 20%
and typically ±8% from 22 to 60 km. The comparisons be-
tween 64 and 90 km show very large and variable differences
(not shown). Note, however, that the error bars, which repre-
sent the uncertainty in the mean difference, often cross zero.
Thus, for much of the altitude range between 64 and 100 km,
the statistical differences are not significant. Part of the prob-
lem here is that so few of the measurements are predicted
to have errors smaller than 100%. Overall, there is a sug-
gestion that the ACE-FTS NO measurements are biased low
with respect to HALOE above 64 km but below 90 km, but
this should be considered a tentative conclusion.
6.3 Ground-based NO from FTIRs
For the validation of ACE-FTS NO, data were available from
all the FTIR stations used for the NO2 comparisons (see
Table 1) except for Bremen. The same analysis has been ap-plied here as in Sect. 5.3. Table 4 shows the ranges where
the sensitivity for the FTIR measurements were greater than
0.5 and for which ACE-FTS data were available. The par-
tial columns were calculated over altitude ranges between
approximately 20 and 45 km. The DOFS are indicated in Ta-
ble 4. Kiruna and Izana are showing DOFS larger than one:
1.6 and 1.3, respectively, while the DOFS of the three other
stations are ∼1. For the NO comparisons, averaging kernels
for Kiruna and Izana were available so that all coincident
ACE-FTS profiles could be smoothed using the method de-
scribed in Sect. 5.3. Then the ACE-FTS data were adjusted
to match the local times of the FTIR stations using the pho-
tochemical box model.
Table 4 lists the mean relative differences between ACE-
FTS and the ground-based FTIR partial columns. The agree-
ment is not very good: there is a consistent low bias in the
ACE-FTS partial columns, ranging from −14.5% for Wollon-
gong to −67.5% for Ny Alesund). The average difference forall stations is −47% with σ =30%.
One possible explanation for this discrepancy is that at
high latitudes during winter and spring there can be high lev-
els of NO in the upper atmosphere that contribute to the FTIR
stratospheric partial columns, but not to the ACE-FTS par-
tial columns, as the retrieval grid and the model atmospheres
of the ground-based stations extend only to 100 km (Wiacek
et al., 2006). This affects Kiruna and Ny Alesund the most,
which have the largest bias compared with the other stations.
We also expect a low bias for the ACE-FTS, because of the
diurnal effect, of about 10%, which is not enough to account
for the large differences observed.A weak correlation between ACE-FTS and the FTIR par-
tial columns is seen in the scatter plot of the data from all
stations. Figure 38 shows a correlation coefficient, r=0.59,
while the line fitted to the ACE-FTS versus FTIR data has
slope 0.52 and intercept 0.31×1015 molec/cm2. The small
slope indicates that the smoothed ACE-FTS partial columns
do not vary sufficiently, i.e. it looks as if they are relatively
constant.
7 Summary and conclusions
An assessment of the quality of the ACE-FTS version 2.2NO2 and NO and MAESTRO version 1.2 NO2 data has been
presented in this paper. NO2 and NO are two of the 14 base-
line species for the ACE mission. Version 2.2 ACE-FTS
VMR profiles are retrieved from solar occultation measure-
ments for NO between 15 and 110 km and for NO2 between
13 and 58 km at a vertical resolution of about 3 to 4 km. Ver-
sion 1.2 MAESTRO data are retrieved from solar occultation
measurements in the wavelength range 420 to 545 nm with a
resolution of 1 to 2 km.
ACE NO2 profiles from the first three years of the mis-
sion have been compared with coincident measurements
made by the HALOE, SAGE II, SAGE III, POAM III, SCIA-MACHY (solar occultations), GOMOS, OSIRIS and MIPAS
satellite instruments, individual balloon flights of SPIRALE
and SAOZ, and ground-based UV-VIS spectrometers (re-
trieved profiles). MAESTRO comparisons with SAGE III
and POAM III were previously performed by Kar et al.
(2007). No MAESTRO comparisons with GOMOS and MI-
PAS were available for this study. ACE-FTS NO profiles
have been compared with HALOE. For MIPAS, a compos-
ite of NO and NO2, NOx, has been compared with ACE-
FTS, because a photochemical model accounting for polar
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T. Kerzenmacher et al.: Validation of NO2 and NO from ACE 5831
Table 6. Summary of results of the NO2 statistical profile comparisons between ACE-FTS, MAESTRO and the correlative measurements.
For cases when the sunrise (SR) and sunset (SS) comparisons were performed separately, this is shown in column 1. The number of
coincidences is given in column 2. Columns 3 to 7: for ACE-FTS, altitude range for valid results, absolute (typical, column 4; maximum,
column5) and relative (typical, column 6; maximum, column 7) differences in this range. Columns 8 to 12: same information for MAESTRO.
ACE-FTS MAESTRO
Instrument # of Range Absolute diff.: Relative diff.: Range Absolute diff.: Relative diff.:
(data product) pairs [km] [ppbv] [%] [km] [pbv] [%]typical max. typical max. typical max. typical max.
HALOE 36 23–40 −0.70 −0.85 −10% −15.8% 22–43 −0.49 −0.94 −10% −17.0%
41–50 +0.55 +0.65 +20 % +40.0% 43–50 −0.42 −0.79 −45 % −68.1 %
SAGE II (SR/SR)a 148 20–43 +0.80 +1.10 +22% +37.7% 20–42 +1.06 +1.98 +25% +38.7%
(SS/SS) 17 20–40 −0.27 −0.66 −6% −12.6% — — — — —
SAGE IIIb 776/712c 20–44 −0.28 −0.65 −8 % −14.3% 25–40 −0.35 −0.64 −9 % −15.8%
POAM IIIb 295/180c 20–24 −0.30 −0.50 −25 % −38.6% 20–24 −0.30 −0.51 −14 % −24.8%
25–44 ±0.20 −0.59 ±6% +12.8% 25–40 −0.27 −0.43 ±8% −22.7%
SCIAMACHY 372 20–39 −0.15 −0.46 ±4% −11.9% 21–40 +0.21 +0.73 +8 % +13.0 %
GOMOS 6865 23–43 n/a n/a ±10% −10.0% — — — — —
MIPAS 84 24–32 −0.24 −0.57 −8 % −15.5% — — — — —
(ESA) 32–47 −1.40 −1.90 −45 % −7.8 % — — — — —
MIPAS 493 28–44 −3.00 −10.00 −20% −25.5% — — — — —(IMK-IAA)
OSIRIS 543/524c 14–24 ~0 −0.04 ±6% −8.2% 12–24 +0.15 +0.32 +25 % +38.5 %
25–40 −0.60 −0.92 −13% −17.3% 25–42 −0.60 −0.91 −14% −16.7%
DOASd (ACE SR) 13/6c 15–37 +0.20 +0.49 +13 % +23.0% 13–37 +0.45 +0.93 +28 % +39.9%
(ACE SS) 15/11c 15–37 ±0.30 +0.82 +13 % +24.9% 13–37 +0.47 +0.87 +25 % +39.7%
SAOZe 5 12–29 −0.04 −0.07 −11 % −28.2% 12–33 −0.05 −0.09 −6 % −19.8%
29–43 +0.80 +1.10 +19 % +34.6% 33–43 +0.66 +0.71 +18 % +24.7%
a SR/SR for comparisons with ACE-FTS only. For the comparisons with MAESTRO, no separation was made.b For comparisons of MAESTRO with POAM III and SAGE III, results are taken from Kar et al. (2007).c Number of profile pairs for ACE-FTS and MAESTRO, respectively.d Ground-based UV-VIS measurements from Harestua, Norway.e Ground-based UV-VIS measurements from Vanscoy, Canada.
NOx descent was not available. In addition, ACE NO2 par-
tial columns have been compared with measurements by six
ground-based FTIRs. For the comparison of ACE-FTS NO
partial columns, five FTIR stations provided data. In the case
of the lower vertical resolution UV-VIS and FTIR compar-
isons, the ACE VMR profiles were smoothed by the appro-
priate averaging kernels, while the high-resolution SPIRALE
profile was smoothed with a triangular function to match
the ACE-FTS resolution and a Gaussian function to match
the MAESTRO resolution. For the UV-VIS, ground-based
FTIR, balloon and four satellite (GOMOS, OSIRIS, MIPASESA NO2, SCIAMACHY nadir) comparisons, a photochem-
ical box model was employed in order to correct NO2 and
NO to the same local time.
The results of the statistical and individual vertical pro-
file comparisons of NO2 for MAESTRO and ACE-FTS
are summarized in Table 6. Typical values are calculated
using average values. When the averages are close to zero
and hence not so typical, averages of all negative error val-
ues and all positive error values are calculated and the maxi-
mum difference is given. Figures 39 and 40 show all absolute
and relative differences. For the ACE-FTS comparisons, the
mean absolute differences are all within ±1 ppbv between 13
and 40 km (and well within ±0.5 ppbv below 20 km), with the
exception of MIPAS ESA product, for which the difference
is more negative above 33 km. Looking at the mean relative
differences for ACE-FTS and MAESTRO, nearly all of the
satellite measurements agree to within about 20% between
25 and 40 km, again with the exception of MIPAS ESA and
SAGE II. MAESTRO reports larger VMR values than ACE-
FTS in the lower and middle stratosphere (see Fig. 7).
The maximum NO2 VMR occurs between 30 and 35 km;
the agreement in this region is good. Below about 25 km, it
can be seen that the diurnal effect has not been fully cor-
rected and ACE-FTS has a low bias relative to POAM III
at about 23 km, which is also present in other studies (e.g.
Brohede et al., 2007a). Above 40 km, there is a suggestion
of a slight low bias in the ACE-FTS data, although the re-
sults are not consistent for all comparisons. For MAESTRO,
the mean absolute differences are within ±1 ppbv between
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5832 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
−2 −1 0 1 210
15
20
25
30
35
40
45
50
55
HALOESAGE II SRSAGE II SSSAGE IIIPOAM IIISCIAMACHYGOMOS
MIPAS ESAOSIRIS
DOAS HarestuaSAOZ Vanscoy
SPIRALESAOZ−balloon
Absolute DifferencesACE−FTS − VAL [ppbv]
A l t i t u d e [ k m ]
−100 −50 0 50 10010
15
20
25
30
35
40
45
50
55
Relative Differences(ACE−FTS − VAL)/MEAN [%]
Fig. 39. Summary plot for all the comparisons with ACE-FTS NO2. Left panel: Profiles of the mean absolute differences. Right panel:
Profiles of the mean relative differences. In both panels, satellite comparisons are indicated by solid lines and other profile comparisons are
indicated by dashed lines. Highlighted in yellow are the ±20% relative differences. Note that for SAGE II the results are separated into
sunrise and sunset profiles. GOMOS is only present in the right hand panel, because no VMRs are available (number densities were used).
13 and 40 km (with the exception of the comparisons with
SAGE II) and within ±0.5 ppbv below 20 km. The mean rel-ative differences for MAESTRO are all within 20% between
25 and 40 km, with the exception of the Harestua UV-VIS
data and the SAGE II data.
It can be seen from the statistical comparisons in Figs. 39
and 40 that there is a systematic low bias between 25 and
35 km for both ACE-FTS and MAESTRO when SAGE II,
POAM III, SCIAMACHY for MAESTRO and the ground-
based profile results are ignored. The shape of the bias is the
same in the HALOE, SAGE III, POAM III, SCIAMACHY
and OSIRIS comparisons. Only SAGE II shows different re-
sults among the solar occultation measurements, but this in-
strument is generally considered less accurate than SAGE III,with SAGE II sunset measurements known to be much better
than the sunrise ones.
Since the random errors for the ACE instruments are very
small, combined random errors are dominated by those of
the comparison instruments. The combined random errors
for the ACE instruments with OSIRIS and MIPAS ESA were
compared to the standard deviation of the relative differ-
ences of the ACE instruments with OSIRIS and MIPAS ESA.
The combined random errors of the ACE instruments with
OSIRIS were found to be around 6 to 19% compared to the
standard deviation in the relative differences of 15 to 55%
and with MIPAS ESA, the combined random errors were 50to 70% compared to the standard deviation of 30 to 78%.
Comparisons were also made with single profiles obtained
from three balloon flights, and are included in Figs. 39 and
40. Of these, the comparison with the in situ SPIRALE mea-
surement shows the biggest difference, with both ACE in-
struments showing a high bias. A likely explanation is that
the assumption of spatial homogeneity of the stratospheric
layers crossed by the lines-of-sight of the satellite instru-
ments is not valid in case of a perturbed dynamical situ-
ation such as that experienced in the high latitude winter.
The SAOZ balloon comparisons are good to within 20% for
the Aire-sur-l’Adour–MAESTRO comparisons, but differ-ences vary between 5% and 50% for ACE-FTS. Even though
the SAOZ balloon profiles from Niamey were taken over a
longer time span, they all agree to within 20% with the ACE-
FTS measurements. MAESTRO and SAOZ balloon mea-
surements agree to within 50%. Below ∼17 km the agree-
ment is not as good. This is probably due to the fact that
the measurements took place during strong convective ac-
tivity that extended up to 17 km and possibly generated NOx
due to lightning. The ground-based UV-VIS profile compar-
isons with data from Harestua agree to within 25% (ACE-
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T. Kerzenmacher et al.: Validation of NO2 and NO from ACE 5833
−2 −1 0 1 210
15
20
25
30
35
40
45
50
55
HALOESAGE IISAGE IIIPOAM III
SCIAMACHYOSIRIS
DOAS HarestuaSAOZ Vanscoy
SPIRALESAOZ−balloon
Absolute DifferencesMAESTRO − VAL [ppbv]
A l t i t u d e [ k m ]
−100 −50 0 50 10010
15
20
25
30
35
40
45
50
55
Relative Differences(MAESTRO − VAL)/MEAN [%]
Fig. 40. Same as Fig. 39 but for MAESTRO. The SAGE III and POAM III results are taken from Kar et al. (2007). For SAGE II, results from
the combined sunrise and sunset comparisons are shown.
FTS) and 40% (MAESTRO), and for Vanscoy to within 35%
(ACE-FTS) and 25% (MAESTRO).
The SCIAMACHY nadir total columns of NO2 showedgood correlations with the partial columns of the ACE in-
struments: r=0.94 for ACE-FTS and r=0.91 for MAE-
STRO. The slopes are 0.77 (ACE-FTS) and 0.79 (MAE-
STRO) and the intercepts are 0.18×1015 molec/cm2 (ACE-
FTS) and 0.38×1015 molec/cm2 (MAESTRO). The observed
differences are of the order expected for the tropospheric
NO2, which is included in the SCIAMACHY columns but
not in ACE partial columns.
The last set of comparisons with NO2 was done with par-
tial columns measured by the ground-based FTIRs. Agree-
ment here is good: the mean relative differences are within
±12% for five of the six stations for comparisons with ACE-FTS and for four stations for comparisons with MAESTRO.
The MAESTRO mean differences are all positive, indicat-
ing that there is a high bias whereas for ACE-FTS this
mean relative difference does not show a bias. A good
correlation (r=0.91) is observed between the ACE-FTS and
FTIR partial columns, with a slope of 0.95 and an inter-
cept of 0.21×1015 molec/cm2. Good correlation (r=0.89)
is also observed between the MAESTRO and FTIR par-
tial columns, with a slope of 1.02 and an intercept of
0.21×1015 molec/cm2.
There are fewer comparisons available to assess the quality
of the ACE-FTS NO VMRs. Tables 4 and 7 show summaries
for the results for the NO and NOx comparisons of ACE-
FTS with ground-based instruments and satellites. It can be
seen that the satellite comparison with HALOE shows a very
good agreement, typically ±8% (and within 20.6%) between
22 and 64 km, and typically +10% (and within 36%) from 93
to 105 km. There is a small low bias in the ACE-FTS NO
measurements below 50 km and a high bias above. The com-
parisons with MIPAS IMK-IAA NOx show typical relative
differences of ±10% (maximum −30.8%) from 15 to 42 km,
and −20% (maximum −52.5%) from 42 to 60 km. Given the
high variability at the time when coincidences were available
this agreement is very good.
For the comparisons of ACE-FTS NO with partial
columns measured by the ground-based FTIRs the agreementis not as good. The mean relative differences are all negative,
having values between −14.5% and −67.5%, and increasing
(becoming more negative) from South to North. This in-
dicates a low bias in the ACE-FTS partial columns relative
to the FTIRs. The correlation is poor (r=0.59) between the
ACE-FTS and FTIR NO partial columns, with a slope of 0.52
and an intercept of 0.31×1015 molec/cm2 on the line fitted to
the data.
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5834 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
Table 7. Summary of results of the NO and NOx statistical comparisons between ACE-FTS and the correlative measurements. The number
of coincidences is given in column 2. Columns 3 to 7: altitude range for valid results, absolute (typical value, column 4; maximum value,
column 5) and relative (typical, column 6; maximum, column 7) differences in this range.
Instrument # of Range Absolute diff.: Relative diff.:
(data product) pairs [km] [ppbv] [%]
typical max. typical max.
MIPAS NOx (IMK-IAA) 493 15–42 −1 −3.7 ±10 % −30.8%
42–60 ±15 −46.4 −20 % −52.5 %
HALOE 36 22–64 ±0.6 −1.1 ±8 % +20.6 %
93–105 +3100 +5640 +10 % +36.0 %
In summary, it has been found that the ACE-FTS version
2.2 NO2 and NO and the MAESTRO version 1.2 NO2 are
generally consistent with other satellite data. The ACE-FTS
and MAESTRO NO2 VMRs agree with the other satellite
data sets (with the exception of MIPAS ESA (for ACE-FTS)
and SAGE II (for ACE- FTS (sunrise) and MAESTRO)) towithin about 20% between 25 and 40 km, and show a neg-
ative bias between 23 and 40 km of about 10%. In compar-
isons with HALOE, ACE-FTS NO VMRs typically agree to
±8% for 22 to 64 km (maximum 21%) and to +10% for 93
to 105 km (maximum 36%). Partial column comparisons for
NO2 show that there is quite good agreement between the
ACE instruments and the FTIRs, with a mean difference of
+7.3% for ACE-FTS and +12.8% for MAESTRO.
Acknowledgements. Funding for the ACE mission was provided
primarily by the Canadian Space Agency (CSA) and the Natural
Sciences and Engineering Research Council (NSERC) of Canada.
This work was also supported by a grant from the CSA. The MAE-STRO instrument was developed with additional financial support
from Environment Canada, the Canadian Foundation for Climate
and Atmospheric Sciences (CFCAS) and NSERC.
Odin is a Swedish-led satellite project funded jointly by the Swedish
National Space Board (SNSB), the CSA, the Centre National
d’Etudes Spatiales (CNES) in France and the National Technology
Agency of Finland (Tekes).
Work at the Jet Propulsion Laboratory (JPL), California Institute of
Technology (CalTech), is carried out under contract with the Na-
tional Aeronautics and Space Administration. For the HALOE,
POAM III, SAGE II and SAGE III comparisons, Lynn Harvey pro-
cessed all the ACE data. NASA grant NNG04GF39G was used to
support the comparisons for these satellites. Thanks to the POAM
team at the US Naval Research Lab for providing the POAM III
data. The authors thank the HALOE Science and Data Processing
Teams for providing the profiles used in this work.
We acknowledge the European Space Agency (ESA) for providing
the MIPAS level 1 and 2 data sets. The IAA team was supported
by the Spanish project ESP2004-01556 and EC FEDER funds.
Thanks to T. von Clarmann, N. Glatthor, U. Grabowski, S. Kell-
mann, M. Kiefer, A. Linden, M. Milz, T. Steck and H. Fischer from
the MIPAS team for their support.The present study was funded at BIRA-IASB by the PRODEX 8
contracts SADE, ACE, and NOy-Bry under the authority of the Bel-
gian Space Science Office (BELSPO).
The SPIRALE balloon measurements could only be per-
formed thanks to the technical team (C. Robert, L. Pomathiod,
B. Gaubicher, G. Jannet); the flight was funded by ESA and French
space agency CNES for the Envisat validation project; the CNES
balloon launching team is greatly acknowledged for successful op-
erations. A. Hauchecorne is acknowledged for making available the
use of MIMOSA advection model and F. Coquelet for useful help
in the potential vorticity calculations and ACE data formatting.
The SAOZ ground-based and balloon operations are supported by
the French CNRS and CNES programme of Atmospheric Chem-istry (PNCA). The flights in Niger are part of the SCOUT-O3
project of the European Commission (contract 505390-GOCE-CT-
2004).
All of the ground-based FTIR stations operate within the
framework of the Network for the Detection of Atmospheric
Composition Change (NDACC, see http://www.ndacc.org ), and
are nationally funded and supported. The European ground-based
FTIR stations have been supported partly by the EU project
UFTIR (http://www.nilu.no/uftir). The Ny Alesund and Bremen
analyses were done within the EU-projects GEOMON and HYMN.
The support by the local IRF Kiruna staff is highly appreciated.
Work at the Toronto Atmospheric Observatory was supported by
NSERC, CSA, CFCAS, ABB Bomem, the Canadian Foundationfor Innovation, the Ontario Research and Development Challenge
Fund, the Premier’s Excellence Research Award and the University
of Toronto.
Edited by: T. Wagner
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T. Kerzenmacher et al.: Validation of NO2 and NO from ACE 5835
References
Abrams, M. C., Chang, A. Y., Gunson, M. R., Abbas, M. M., Gold-
man, A., Irion, F. W., Michelsen, H. A., Newchurch, M. J., Rins-
land, C. P., Stiller, G. P., and Zander, R.: On the assessment and
uncertainty of atmospheric trace gas burden measurements with
high resolution infrared solar occultation spectra from space by
the ATMOS experiment, Geophys. Res. Lett., 23, 2337–2340,
doi:10.1029/96GL01794, 1996.
Ackermann, M. and Muller, C.: Stratospheric Nitrogen Dioxide
from Infrared Absorption Spectra, Nature, 240, 300–301, 1972.
Amekudzi, L. K., Sinnhuber, B.-M., Sheode, N. V., Meyer, J.,
Rozanov, A., Lamsal, L. N., Bovensmann, H., and Burrows, J. P.:
Retrieval of stratospheric NO3 vertical profiles from sciamachy
lunar occultation measurement over the Antarctic, J. Geophys.
Res., 110, D20304, doi:10.1029/2004JD005748, 2005.
Amekudzi, L. K., Bramstedt, K., Bracher, A., Rozanov, A., Bovens-
mann, H., and Burrows, J. P.: SCIAMACHY solar and lu-
nar occultation: validation of ozone, NO2 and NO3 profiles,
in: Proc. of Atmospheric Chemistry Validation (ACVE-3) De-
cember 2006, SP-642, ESA Publication Division, ESTEC, No-
ordwijk, The Netherlands, http://www.sciamachy.org/validation/ documentation/proceedings ACVE-3/amekudzi.pdf, 2007.
Bernath, P. F.: Atmospheric chemistry experiment (ACE): Ana-
lytical chemistry from orbit, Trend. Anal. Chem., 25, 647–654,
2006.
Bernath, P. F., McElroy, C. T., Abrams, M. C., Boone, C. D., Butler,
M., Camy-Peyret, C., Carleer, M., Clerbaux, C., Coheur, P.-F.,
Colin, R., DeCola, P., De Maziere, M., Drummond, J. R., Dufour,
D., Evans, W. F. J., Fast, H., Fussen, D., Gilbert, K., Jennings, D.
E., Llewellyn, E. J., Lowe, R. P., Mahieu, E., McConnell, J. C.,
McHugh, M., McLeod, S. D., Michaud, R., Midwinter, C., Nas-
sar, R., Nichitiu, F., Nowlan, C., Rinsland, C. P., Rochon, Y. J.,
Rowlands, N., Semeniuk, K., Simon, P., Skelton, R., Sloan, J. J.,
Soucy, M.-A., Strong, K., Tremblay, P., Turnbull, D., Walker, K.
A., Walkty, I., Wardle, D. A., Wehrle, V., Zander, R., and Zou, J.:
Atmospheric Chemistry Experiment (ACE): Mission overview,
Geophys. Res. Lett., 32, L15S01, doi:10.1029/2005GL022386,
2005.
Berthet, G., Renard, J.-B., Catoire, V., Chartier, M., Robert, C.,
Huret, N., Coquelet, F., Bourgeois, Q., Riviere, E. D., Barret,
B., Lef evre, F., and Hauchecorne, A.: Remote-sensing measure-
ments in the polar vortex: Comparison to in situ observations
and implications for the simultaneous retrievals and analysis of
the NO2 and OClO species, J. Geophys. Res., 112, D21310,
doi:10.1029/2007JD008699, 2007.
Blumenstock, T., Kopp, G., Hase, F., Hochschild, G., Mikuteit, S.,
Raffalski, U., and Ruhnke, R.: Observation of unusual chlorine
activation by ground-based infrared and microwave spectroscopyin the late Arctic winter 2000/01, Atmos. Chem. Phys., 6, 897–
905, 2006, http://www.atmos-chem-phys.net/6/897/2006/.
Boone, C. D., Nassar, R., Walker, K. A., Rochon, Y., McLeod, S.
D., Rinsland, C. P., and Bernath, P. F.: Retrievals for the Atmo-
spheric Chemistry Experiment Fourier-transform spectrometer,
Appl. Optics, 44, 7218–7231, 2005.
Bovensmann, H., Burrows, J. P., Buchwitz, M., Frerick, J., Noel,
S., Rozanov, V. V., Chance, K. V., and Goede, A. P. H.: SCIA-
MACHY: Mission Objectives and Measurement Modes, J. At-
mos. Sci., 56, 127–150, 1999.
Bracher, A., Bovensmann, H., Bramstedt, K., Burrows, J., von
Clarmann, T., Eichmann, K.-U., Fischer, H., Funke, B., Gil-
Lopez, S., Glatthor, N., Grabowski, U., Hopfner, M., Kauf-
mann, M., Kellmann, S., Kiefer, M., Koukouli, M., Linden, A.,
Lopez-Puertas, M., Tsidu, G. M., Milz, M., Noel, S., Rohen,
G., Rozanov, A., Rozanov, V., von Savigny, C., Sinnhuber, M.,
Skupin, J., Steck, T., Stiller, G., Wang, D.-Y., Weber, M., and
Wuttke, M.: Cross comparisons of O3 and NO2 measured by
the atmospheric ENVISAT instruments GOMOS, MIPAS, and
SCIAMACHY, Adv. Space Res., 36, 855–867, 2005.
Bracher A., Sinnhuber M., Rozanov A., and Burrows J.P.: Using
a photochemical model for the validation of NO2 satellite mea-
surements at different solar zenith angles, Atmos. Chem. Phys.,
5, 393–408, 2005,
http://www.atmos-chem-phys.net/5/393/2005/.
Bramstedt, K., Amekudzi, L. K., Bracher, A., Rozanov, A., Bovens-
mann, H., and Burrows, J. P.: SCIAMACHY solar occultation:
Ozone and NO2 profiles from 2002–2006, in: Proc. of Envisat
Symposium 2007, SP-636, ESA Publication Division, ES-
TEC, Noordwijk, The Netherlands, http://www.sciamachy.org/
validation/documentation/proceedings ES2007/463231br.pdf,
2007.
Brewer, A. W., McElroy, C. T., and Kerr, J. B.: Nitrogen diox-ide concentrations in the atmosphere, Nature, 246, 129–133,
doi:10.1038/246129a0, 1973.
Brohede, S. M., Haley, C. S., McLinden, C. A., Sioris, C. E.,
Murtagh, D. P., Petelina, S. V., Llewellyn, E. J., Bazureau, A.,
Goutail, F., Randall, C. E., Lumpe, J. D., Taha, G., Thomas-
son, L. W., and Gordley, L. L.: Validation of Odin/OSIRIS
stratospheric NO2 profiles, J. Geophys. Res., 112, D07310,
doi:10.1029/2006JD007586, 2007a.
Brohede, S. M., McLinden, C. A., Berthet, G., Haley, C. S.,
Murtagh, D., and Sioris, C. E.: A stratospheric NO2 climatology
from Odin/OSIRIS limb-scatter measurements, Can. J. Phys., 85,
1253–1274, doi:10.1139/P07-141, 2007b.
Buchwitz, M., Schneising, O., Burrows, J. P., Bovensmann, H.,
Reuter, M., and Notholt, J.: First direct observation of the at-
mospheric CO2 year-to-year increase from space, Atmos. Chem.
Phys., 7, 4249–4256, 2007,
http://www.atmos-chem-phys.net/7/4249/2007/ .
Burkhardt, E. G., Lambert, C. A., and Patel, C. K. N.: Stratospheric
nitric oxide: Measurements during daytime and sunset, Science,
188, 1111–1113, 1975.
Burrows, J. P., Dehn, A., Deters, B., Himmelmann, S., Richter, A.,
Voigt, S., and Orphal, J.: Atmospheric remote-sensing reference
data from GOME: 1. Temperature-dependent absorption cross-
sections of NO2 in the 231–794 nm range, J. Quant. Spectrosc.
Ra., 60, 1025–1031, 1998.
Burrows, J. P., Weber, M., Buchwitz, M., Rozanov, V., Ladst atter-
Weißenmayer, A., Richter, A., Debeek, R., Hoogen, R., Bram-stedt, K., Eichmann, K.-U., Eisinger, M., and Perner, D.: The
Global Ozone Monitoring Experiment (GOME): Mission Con-
cept and First Scientific Results, J. Atmos. Sci., 56, 151–175,
1999.
Callies, J., Corpaccioli, E., Eisinger, M., Lefebvre, A., Munro,
R., Perez-Albinana, A., Ricciarelli, B., Calamai, L., Gironi, G.,
Veratti, R., Otter, G., Eschen, M., and van Riel, L.: GOME-2
ozone instrument onboard the European METOP satellites,
in: Weather and Environmental Satellites, vol. 5549 of Proc.
SPIE Int. Soc. Opt. Eng., 60–70, doi:10.1117/12.557860,
www.atmos-chem-phys.net/8/5801/2008/ Atmos. Chem. Phys., 8, 5801–5841, 2008
8/2/2019 T. Kerzenmacher et al- Validation of NO2 and NO from the Atmospheric Chemistry Experiment (ACE)
http://slidepdf.com/reader/full/t-kerzenmacher-et-al-validation-of-no2-and-no-from-the-atmospheric-chemistry 36/41
8/2/2019 T. Kerzenmacher et al- Validation of NO2 and NO from the Atmospheric Chemistry Experiment (ACE)
http://slidepdf.com/reader/full/t-kerzenmacher-et-al-validation-of-no2-and-no-from-the-atmospheric-chemistry 37/41
T. Kerzenmacher et al.: Validation of NO2 and NO from ACE 5837
Space Shuttle missions, Geophys. Res. Lett., 23, 2333–2336,
1996.
Haley, C. S. and Brohede, S.: Status of the Odin/OSIRIS
Stratospheric O3 and NO2 Data Products, Can. J. Phys., 85,
doi:10.1139/P07-114, 2007.
Haley, C. S., Brohede, S. M., Sioris, C. E., Griffioen, E., Murtagh,
D. P., McDade, I. C., Eriksson, P., Llewellyn, E. J., Bazureau,
A., and Goutail, F.: Retrieval of stratospheric O3
and NO2
pro-
files from Odin Optical Spectrograph and Infrared Imager Sys-
tem (OSIRIS) limb-scattered sunlight measurements, J. Geo-
phys. Res., 109(D16), doi:10.1029/2004JD004588, 2004.
Hase, F.: Inversion von Spurengasprofilen aus hochaufgelosten
bodengebundenen FTIR-Messungen in Absorption, in:
Wissenschaftliche Berichte, no. 6512 in FZK Report,
Forschungszentrum Karlsruhe, ISSN 0947–8620, 2000.
Hase, F., Hannigan, J. W., Coffey, M. T., A., G., H opfner, M., Jones,
N. B., Rinsland, C. P., and Wood, S. W.: Intercomparison of
retrieval codes used for the analysis of high-resolution, ground-
based FTIR measurements, J. Quant. Spectrosc. Ra., 87, 25–52,
2004.
Hase, F., Demoulin, P., Sauval, A., Toon, G., Bernath, P., Gold-
man, A., Hannigan, J., and Rinsland, C.: An empirical line-by-line model for the infrared solar transmittance spectrum from
700 to 5000cm−1, J, Quant. Spectros. Ra., 102, 450–463,
doi:10.1016/j.jqsrt.2006.02.026, 2006.
Hauchecorne, A., Godin, S., Marchand, M., Heese, B., and
Souprayen, C.: Quantification of the transport of chemical con-
stituents from the polar vortex to midlatitudes in the lower
stratosphere using the high-resolution advection model MI-
MOSA and effective diffusivity, J. Geophys. Res., 107, 8289,
doi:10.1029/2001JD000491, 2002.
Hauchecorne, A., Bertaux, J.-L., Dalaudier, F., Russell III, J. M.,
Mlynczakand, M. G., Kyrola, E., and Fussen, D.: Large in-
crease of NO2 in the north polar mesosphere in January–
February 2004: Evidence of a dynamical origin from GO-
MOS/ENVISAT and SABER/TIMED data, Geophys. Res. Lett.,
34(L03), 810, doi:10.1029/2006GL027628, 2007.
Hendrick, F., Barret, B., van Roozendael, M., Boesch, H., Butz,
A., De Maziere, M., Goutail, F., Hermans, C., Lambert, J.-C.,
Pfeilsticker, K., and Pommereau, J.-P.: Retrieval of nitrogen
dioxide stratospheric profiles from ground-based zenith-sky UV-
visible observations: Validation of the technique through correl-
ative comparisons, Atmos. Chem. Phys., 4, 2091–2106, 2004,
http://www.atmos-chem-phys.net/4/2091/2004/.
Hendrick, F., Granville, J., Lambert, J.-C., and van Roozen-
dael, M.: Validation of SCIAMACHY OL3.0 NO2 Profiles
and Columns Using Ground-Based DOAS Profiling, in: Pro-
ceedings of the Third Workshop on the Atmospheric Chem-
istry Validation of Envisat (ACVE-3), ESA-ESRIN, Fras-cati, Italy, http://www.sciamachy.org/validation/documentation/
proceedings ACVE-3/hendrick.pdf, ESA SP-642, 2007.
Irie, H., Kondo, Y., Koike, M., Danilin, M. Y., Camy-Peyret, C.,
Payan, S., Pommereau, J. P., Goutail, F., Oelhaf, H., Wetzel, G.,
Toon, G. C., Sen, B., Bevilacqua, R. M., Russell III, J. M., Re-
nard, J. B., Kanzawa, H., Nakajima, H., Yokota, T., Sugita, T.,
and Sasano, Y.: Validation of NO2 and HNO3 measurements
from the Improved Limb Atmospheric Spectrometer (ILAS) with
the version 5.20 retrieval algorithm, J. Geophys. Res., 107, 8206,
doi:10.1029/2001JD001304, 2002.
Kar, J., McElroy, C. T., Drummond, J. R., Zou, J., Nichitiu, F.,
Walker, K. A., Randall, C. E., Nowlan, C. R., Dufour, D. G.,
Boone, C. D., Bernath, P. F., Trepte, C. R., Thomason, L. W., and
McLinden, C.: Initial Comparison of Ozone and NO2 profiles
from ACE-MAESTRO with Balloon and Satellite Data, J. Geo-
phys. Res., 112(D16), 301, doi:10.1029/2006JD008242, 2007.
Kerzenmacher, T., Walker, K. A., Strong, K., Berman, R., Bernath,
P. F., Boone, C. D., Drummond, J. R., Fast, H., Fraser, A.,
MacQuarrie, K., Midwinter, C., Sung, K., McElroy, C. T., Mit-
termeier, R. L., Walker, J., and Wu, H.: Measurements of
O3, NO2 and Temperature during the 2004 Canadian Arctic
ACE Validation Campaign, Geophys. Res. Lett., 32, L16S07,
doi:10.1029/2005GL023032, 2005.
Kleinert, A., Aubertin, G., Perron, G., Birk, M., Wagner, G.,
Hase, F., Nett, H., and Poulin, R.: MIPAS Level 1B algorithms
overview: operational processing and characterization, Atmos.
Chem. Phys., 7, 1395–1406, 2007,
http://www.atmos-chem-phys.net/7/1395/2007/ .
Kouker, W., Langbein, I., Reddmann, T., and Ruhnke, R.: The Karl-
sruhe simulation model of the middle atmosphere (KASIMA),
version 2, Tech. Rep. 6278, Forschungszentrum Karlsruhe, 1999.
Kyrola, E., Tamminen, J., Leppelmeier, G. W., Sofieva, V., Hassi-nen, S., Bertaux, J.-L., Hauchecorne, A., Dalaudier, F., Cot, C.,
Korablev, O., Hembise, O., Barrot, G., Mangin, A., Theodore,
B., Guirlet, M., Etanchaud, F., Snoeij, P., Koopman, R., Saave-
dra, L., Fraisse, R., Fussen, D., and Vanhellemont, F.: GO-
MOS on Envisat: An overview, Adv. Space Res., 33, 1020–1028,
doi:10.1016/S0273-1177(03)00590-8, 2004.
Lambert, J., Van Roozendael, M., Simon, P., Pommereau, J.,
Goutail, F., Gleason, J., Andersen, S., Arlander, D., Buivan, N.,
Claude, H., De La Noe, J., De Maziere, M., Dorokhov, V., Erik-
sen, P., Green, A., Karlsen Tornqvist, K., Kastadt Hoiskar, B.,
Kyro, E., Leveau, J., Merienne, M., Milinevsky, G., Roscoe, H.,
Sarkissian, A., Shanklin, J., Staehelin, J., Wahlstrom Tellefsen,
C., and Vaughan, G.: Combined characterization of GOME and
TOMS total ozone measurements from space using ground-based
observations from the NDSC, Adv. Space Res., 26, 1931–1940,
2001.
Lambert, J.-C., Roozendael, M. V., Maziere, M. D., Simon, P. C.,
Pommereau, J.-P., Goutail, F., Sarkissian, A., and Gleason, J.
F.: Investigation of to pole-to pole performances of space-borne
atmospheric chemistry sensors with ground-based networks, J.
Atmos. Sci., 56, 176–193, 1999.
Lefevre, F., Figarol, F., Carslaw, K., and Peter, T.: The 1997 Arctic
ozone depletion quantified from three-dimensional model simu-
lations, Geophys. Res. Lett., 25, 2425–2428, 1998.
Levelt, P. F., van den Oord, G. H. J., Dobber, M. R., Mlkki, A.,
Visser, H., de Vries, J., Stammes, P., Lundell, J. O. V., and Saari,
H.: The Ozone Monitoring Instrument, IEEE Trans. Geosci. Re-mote Sens., 44, 1093–1101, 2006.
Llewellyn, E. J., Lloyd, N. D., Degenstein, D. A., Gattinger, R.
L., Petelina, S. V., Bourassa, A. E., Wiensz, J. T., Ivanov, E. V.,
McDade, I. C., Solheim, B. H., McConnell, J. C., Haley, C. S.,
von Savigny, C., Sioris, C. E., McLinden, C. A., Griffioen, E.,
Kaminski, J., Evans, W. F. J., Puckrin, E., Strong, K., Wehrle, V.,
Hum, R. H., Kendall, D. J. W., Matsushita, J., Murtagh, D. P.,
Brohede, S., Stegman, J., Witt, G., Barnes, G., Payne, W. F.,
Piche, L., Smith, K., Warshaw, G., Deslauniers, D.-L., Marc-
hand, P., Richardson, E. H., King, R. A., Wevers, I., McCreath,
www.atmos-chem-phys.net/8/5801/2008/ Atmos. Chem. Phys., 8, 5801–5841, 2008
8/2/2019 T. Kerzenmacher et al- Validation of NO2 and NO from the Atmospheric Chemistry Experiment (ACE)
http://slidepdf.com/reader/full/t-kerzenmacher-et-al-validation-of-no2-and-no-from-the-atmospheric-chemistry 38/41
5838 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
W., Kyrola, E., Oikarinen, L., Leppelmeier, G. W., Auvinen, H.,
Megie, G., Hauchecorne, A., Lefevre, F., de La Noe, J., Ricaud,
P., Frisk, U., Sjoberg, F., von Scheele, F., and Nordh, L.: The
OSIRIS instrument on the Odin spacecraft, Can. J. Phys., 82,
411–422, 2004.
Lopez-Puertas, M., Funke, B., Gil-Lopez, S., von Clarmann, T.,
Stiller, G. P., Hopfner, M., Kellmann, S., Fischer, H., and Jack-
man, C. H.: Observation of NOx
Enhancement and Ozone De-
pletion in the Northern and Southern Hemispheres after the
October-November 2003 Solar Proton Events, J. Geophys. Res.,
110, A09S43, doi:10.1029/2005JA011050, 2005.
Lucke, R. L., Korwan, D. R., Bevilacqua, R. M., Hornstein, J. S.,
Shettle, E. P., Chen, D. T., Daehler, M., Lumpe, J. D., Fromm, M.
D., Debrestian, D., Neff, B., Squire, M., Konig-Langlo, G., and
Davies, J.: The Polar Ozone and Aerosol Measurement (POAM)
III instrument and early validation results, J. Geophys. Res., 104,
18 785–18 800, doi:10.1029/1999JD900235, 1999.
Manney, G. L., Michelsen, H. A., Santee, M. L., Gunson, M.
R., Irion, F. W., Roche, A. E., and Livesey, N. J.: Polar
vortex dynamics during spring and fall diagnosed using trace
gas observations from the Atmospheric Trace Molecule Spec-
troscopy instrument, J. Geophys. Res., 104, 18 841–18469,doi:10.1029/1999JD900317, 1999.
Manney, G. L., Daffer, W. H., Zawodny, J. M., Bernath, P. F.,
Hoppel, K. W., Walker, K. A., Knosp, B. W., Boone, C. D.,
E., R. E., L., S. M., L., H. V., S., P., R., J. D., L., D., T.,
M. C., A., M. C., Drummond, J. R., Pumphrey, H. C., Lam-
bert, A., Schwartz, M. J., Froidevaux, L., McLeod, S. D., Takacs,
L. L., Suarez, M. J., R., T. C., Cuddy, D. C., Livesey, N. J.,
Harwood, R. S., and Waters, J. W.: Solar occultation satellite
data and derived meteorological products: sampling issues and
comparisons with Aura MLS, J. Geophys. Res., 112, D24S50,
doi:10.1029/2007JD008709, 2007.
Mauldin, L. E. I., Zaun, N. H., McCormick, M. P., Guy, J. H., and
Vaughn, W. R.: Stratospheric Aerosol and Gas Experiment II
instruments: A functional description, Opt. Eng., 24, 307–312,
1985.
Mayer, B. and Kylling, A.: Technical note: The libRadtran software
package for radiative transfer calculations – description and ex-
amples of use, Atmos. Chem. Phys., 5, 1855–1877, 2005,
http://www.atmos-chem-phys.net/5/1855/2005/.
McCormick, M., Hamill, P., Pepin, T., Chu, W., Swissler, T., and
McMaster, L.: Satellite Studies of the Stratospheric Aerosol, B.
Am. Meteorol. Soc., 60, 1038–1046, 1979.
McElroy, C. T.: A spectroradiometer for the measurement of di-
rect and scattered solar spectral irradiance from on-board the
NASA ER-2 high-altitude research aircraft, Geophys. Res. Lett.,
22, 1361–1364, 1995.
McElroy, C. T., Midwinter, C., Barton, D. V., and Hall, R. B.: AComparison of J-values estimated by the composition and pho-
todissociative flux measurement with model calculations, Geo-
phys. Res. Lett., 22, 1365–1368, 1995.
McElroy, C. T., Nowlan, C. R., Drummond, J. R., Bernath, P. F.,
Barton, D. V., Dufour, D. G., Midwinter, C., Hall, R. B., Ogyu,
A., Ullberg, A., Wardle, D. I., Kar, J., Zou, J., Nichitiu, F.,
Boone, C. D., Walker, K. A., and Rowlands, N.: The ACE-
MAESTRO instrument on SCISAT: description, performance,
and preliminary results, Appl. Optics, 46, 4341–4356, 2007.
McHugh, M., Magill, B., Walker, K. A., Boone, C. D., Bernath,
P. F., and Russell III, J. M.: Comparison of atmospheric retrievals
from ACE and HALOE, Geophys. Res. Lett., 32, L10S10,
doi:10.1029/2005GL022403, 2005.
McLinden, C., McConnell, J., Griffioen, E., and McElroy, C. T.:
A vector radiative transfer model for the Odin/OSIRIS project,
Can. J. Phys., 80, 375–393, 2002.
McLinden, C. A., Olsen, S. C., Hannegan, B., Wild, O., Prather, M.
J., and Sundet, J.: Stratospheric ozone in 3-D models: A simple
chemistry and the cross-tropopause flux, J. Geophys. Res., 105,
14 653–14665, 2000.
McLinden, C. A., Haley, C. S., and Sioris, C. E.: Diurnal effects
in limb scatter observations, J. Geophys. Res., 111(D14), 302,
doi:10.1029/2005JD006628, 2006.
Melo, S. M. L., Strong, K., Bassford, M. R., Preston, K. E., McEl-
roy, C. T., Rozanov, E. V., and Egorova, T.: Retrieval of Strato-
spheric NO2 Vertical Profiles from Ground-based Zenith-Sky
DOAS Measurements: Results for the MANTRA 1998 Field
Campaign, Atmos.-Ocean, 43, 339–350, 2005.
Meyer, J., Bracher, A., Rozanov, A., Schlesier, A. C., Bovensmann,
H., and Burrows, J. P.: Solar occultation with SCIAMACHY:
algorithm description and first validation, Atmos. Chem. Phys.,
5, 1589–1604, 2005,http://www.atmos-chem-phys.net/5/1589/2005/ .
Moreau, G., Robert, C., Catoire, V., Chartier, M., Camy-Peyret, C.,
Huret, N., Pirre, M., Pomathiod, L., and Chalumeau, G.: SPI-
RALE: a multispecies in situ balloon-borne instrument with six
tunable diode laser spectrometers, Appl. Optics, 44, 5972–5989,
2005.
Mount, G. H., Rusch, D. W., Zawodny, J. M., Barth, C. A., and
Noxon, J. F.: Measurements of stratospheric NO2 from the Solar
Mesosphere Explorer satellite. I – An overview of the results, J.
Geophys. Res., 89, 1327–1340, 1984.
Murcray, D. G., Kyle, T. G., Murcray, F. H., and Williams, W. J.:
Nitric acid and nitric oxide in the lower stratosphere, Nature, 218,
1968.
Nakajima, H., Sugita, T., Yokota, T., Ishigaki, T., Mogi, Y.,
Araki, N., Waragai, K., Kimura, N., Iwazawa, T., Kuze, A.,
Tanii, J., Kawasaki, H., Horikawa, M., Togami, T., Uemura, N.,
Kobayashi, H., and Sasano, Y.: Characteristics and performance
of the Improved Limb Atmospheric Spectrometer-II (ILAS-II)
on board the ADEOS-II satellite, J. Geophys. Res., 111, D11S01,
doi:10.1029/2005JD006334, 2006.
Newchurch, M. J., Allen, M., Gunson, M. R., Salawitch, R. J.,
Collins, G. B., Huston, K. H., Abbas, M. M., Abrams, M. C.,
Chang, A. Y., Fahey, D. W., Gao, R. S., Irion, F. W., Loewen-
stein, M., Manney, G. L., Michelsen, H. A., Podolske, J. R.,
Rinsland, C. P., and Zander, R.: Stratospheric NO and NO2 abun-
dances from ATMOS solar-occultation measurements, Geophys.
Res. Lett., 23, 2373–2376, 1996.Norton, H. and Beer, R.: New apodizing functions for Fourier spec-
trometry, J. Opt. Soc. Am., 66, 259–264, 1976; errata corrige J.
Opt. Soc. Am., 67, 419, 1977.
Notholt, J., Toon, G., Stordal, F., Solberg, S., Schmidbauer, N.,
Meier, A., Becker, E., and Sen, B.: Seasonal variations of At-
mospheric trace gases in the high Arctic at 79◦ N, J. Geophys.
Res., 102, 12 855–12861, 1997.
Noxon, J. F.: Nitrogen dioxide in the stratosphere and troposphere
measured by ground-based absorption spectroscopy, Science,
187, 547–549, 1975.
Atmos. Chem. Phys., 8, 5801–5841, 2008 www.atmos-chem-phys.net/8/5801/2008/
8/2/2019 T. Kerzenmacher et al- Validation of NO2 and NO from the Atmospheric Chemistry Experiment (ACE)
http://slidepdf.com/reader/full/t-kerzenmacher-et-al-validation-of-no2-and-no-from-the-atmospheric-chemistry 39/41
8/2/2019 T. Kerzenmacher et al- Validation of NO2 and NO from the Atmospheric Chemistry Experiment (ACE)
http://slidepdf.com/reader/full/t-kerzenmacher-et-al-validation-of-no2-and-no-from-the-atmospheric-chemistry 40/41
5840 T. Kerzenmacher et al.: Validation of NO2 and NO from ACE
C. P., Smith, M. A. H., Tennyson, J., Tolchenov, R. N., Toth,
R. A., Vander Auwera, J., Varanasi, P., and Wagner, G.: The HI-
TRAN 2004 molecular spectroscopic database, J. Quant. Spec-
trosc. Ra., 96, 139–204, 2005.
Rozanov, A., Rozanov, V., Buchwitz, M., Kokhanovsky, A., and
Burrows, J. P.: SCIATRAN 2.0 – A new radiative transfer model
for geophysical applications in the 175–2400 nm spectral region,
Adv. Space Res., 36, 1015–1019, 2005.
Russell III, J. M., Gordley, L. L., Park, J. H., Drayson, S. R., Hes-
keth, W. D., Cicerone, R. J., Tuck, A. F., Frederick, J. E., Harries,
J. E., and Crutzen, P. J.: The Halogen Occultation Experiment,
J. Geophys. Res., 98, 10 777–10797, doi:10.1029/93JD00799,
1993.
SAGE ATBD Team: SAGEIII Algorithm Theoretical Basis Doc-
ument (ATBD) for transmission level 1b products version 2.1,
Tech. rep., NASA Langley Res. Cent. (LaRC), Hampton, Vir-
gina, 2002.
Sander, S. P., Friedl, R. R., Golden, D. M., Kuyolo, Huie, R. E.,
Orkin, V. L., Moortgat, G. K., Ravishankara, A. R., Kolb, C. E.,
Molina, M. J., and Finlayson-Pitts, B. J.: Chemical kinetics and
photochemical data for use in stratospheric modeling, in Evalua-
tion 14, Tech. Rep. 02-025, JPL, Pasadena, California, 2003.Sasano, Y., Suzuki, M., Yokota, T., and Kanzawa, H.: Improved
Limb Atmospheric Spectrometer (ILAS) for stratospheric ozone
layer measurements by solar occultation technique, Geophys.
Res. Lett., 26, 197–200, 1999.
Schneider, M., Blumenstock, T., Chipperfield, M., Hase, F., Kouker,
W., Reddmann, T., Ruhnke, R., Cuevas, E., and Fischer, H.:
Subtropical trace gas profiles determined by ground-based FTIR
spectroscopy at Izana (28◦ N, 16◦ W): Five year record, error
analysis, and comparison with 3D-CTMs, Atmos. Chem. Phys.,
5, 153–167, 2005,
http://www.atmos-chem-phys.net/5/153/2005/.
Strong, K., Bailak, G., Barton, D., Bassford, M. R., Blatherwick,
R. D., Brown, S., Chartrand, D., Davies, J., Drummond, J. R., Fo-
gal, P. F., Forsberg, E., Hall, R., Jofre, A., Kaminski, J., Kosters,
J., Laurin, C., McConnell, J. C., McElroy, C. T., McLinden,
C. A., Melo, S. M. L., Menzies, K., Midwinter, C., Murcray, F. J.,
Nowlan, C., Olson, R. J., Quine, B. M., Rochon, Y., Savastiouk,
V., Solheim, B., Sommerfeldt, D., Ullberg, A., Werchohlad, S.,
Wu, H., and Wunch, D.: MANTRA - A Balloon Mission to Study
the Odd-Nitrogen Budget of the Stratosphere, Atmos.-Ocean.,
43, 283–299, 2005.
Strong, K., Wolff, M. A., Kerzenmacher, T. E., Walker, K. A.,
Bernath, P. F., Blumenstock, T., Boone, C., Catoire, V., Coffey,
M., Maziere, M. D., Demoulin, P., Duchatelet, P., Dupuy, E.,
Hannigan, J., Hopfner, M., Glatthor, N., Griffith, D. W. T., Jin,
J., Jones, N., Jucks, K., Kuttippurath, J., Lambert, A., Mahieu,
E., McConnell, J. C., Mellqvist, J., Mikuteit, S., Murtagh, D.,Notholt, J., Piccolo, C., Raspollini, P., Ridolfi, M., Robert, C.,
Schneider, M., Schrems, O., Semeniuk, K., Senten, C., Stiller,
G. P., Strandberg, A., Taylor, J., Tetard, C., Toohey, M., Ur-
ban, J., Warneke, T., and Wood, S.: Validation of ACE-FTS N2O
Measurements, Atmos. Chem. Phys., 8, 4759–4786, 2008,
http://www.atmos-chem-phys.net/8/4759/2008/.
Taylor, F. W., Rodgers, C. D., Whitney, J. G., Werrett, S. T., Bar-
nett, J. J., Peskett, G. D., Venters, P., Ballard, J., Palmer, C.
W. P., Knight, R. J., Morris, P., Nightingale, T., and Dudhia,
A.: Remote sensing of the atmospheric structure and composi-
tion by pressure modulator radiometry from space: the ISAMS
experiment on UARS, J. Geophys. Res., 98, 10 799–10814,
doi:10.1029/92JD03029, 1993.
Vandaele, A. C., Fayt, C., Hendrick, F., Hermans, C., Humbled,
F., van Roozendael, M., Gil, M., Navarro, M., Puentedura, O.,
Yela, M., Braathen, G., Stebel, K., Tørnkvist, K., Johnston, P.,
Kreher, K., Goutail, F., Mieville, A., Pommereau, J.-P., Khaikine,
S., Richter, A., Oetjen, H., Wittrock, F., Bugarski, S., Friess, U.,
Pfeilsticker, K., Sinreich, R., Wagner, T., Corlett, G., and Leigh,
R.: An intercomparison campaign of ground-based UV-Visible
measurements of NO2, BrO, and OClO slant columns. Methods
of analysis and results for NO2, J. Geophys. Res., 110(D08), 305,
doi:10.1029/2004JD005423, 2005.
Vigouroux, C., De Maziere M., Errera, Q, Chabrillat, S., Mahieu,
E., Duchatelet, P., Wood, S., Smale, D., Mikuteit, S., Blumen-
stock, T., Hase, F., and Jones, N.: Comparisons between ground-
based FTIR and MIPAS N2O and HNO3 profiles before and af-
ter assimilation in BASCOE, Atmos. Chem. Phys., 7, 377–396,
2007, http://www.atmos-chem-phys.net/7/377/2007/ .
von Clarmann, T., Chidiezie Chineke, T., Fischer, H., Funke, B.,
Garcıa-Comas, M., Gil-Lopez, S., Glatthor, N., Grabowski, U.,
Hopfner, M., Kellmann, S., Kiefer, M., Linden, A., Lopez-Puertas, M., Lopez-Valverde, M.-A., Mengistu Tsidu, G., Milz,
M., Steck, T., and Stiller, G. P.: Remote Sensing of the Middle
Atmosphere with MIPAS, in: Remote Sensing of Clouds and the
Atmosphere VII, edited by: Schafer, K., Lado-Bordowsky, O.,
Comeron, A., and Picard, R. H., 4882, 172–183, SPIE, Belling-
ham, WA, USA, 2003a.
von Clarmann, T., Glatthor, N., Grabowski, U., Hopfner, M., Kell-
mann, S., Kiefer, M., Linden, A., Mengistu Tsidu, G., Milz,
M., Steck, T., Stiller, G. P., Wang, D. Y., Fischer, H., Funke,
B., Gil-Lopez, S., and Lopez-Puertas, M.: Retrieval of temper-
ature and tangent altitude pointing from limb emission spectra
recorded from space by the Michelson Interferometer for Passive
Atmospheric Sounding (MIPAS), J. Geophys. Res., 108, 4736,
doi:10.1029/2003JD003602, 2003b.
Wetzel, G., Oelhaf, H., Friedl-Vallon, F., Kleinert, A., Lengel,
A., Maucher, G., Nordmeyer, H., Ruhnke, R., Nakajima,
H., Sasano, Y., Sugita, T., and Yokota, T.: Intercompari-
son and validation of ILAS-II version 1.4 target parameters
with MIPAS-B measurements, J. Geophys. Res., 111, D11S06,
doi:10.1029/2005JD006287, 2006.
Wetzel, G., Bracher, A., Funke, B., Goutail, F., Hendrick, F.,
Lambert, J.-C., Mikuteit, S., Piccolo, C., Pirre, M., Bazureau,
A., Belotti, C., Blumenstock, T., De Maziere, M., Fischer, H.,
Huret, N., Ionov, D., Lopez-Puertas, M., Maucher, G., Oel-
haf, H., Pommereau, J.-P., Ruhnke, R., Sinnhuber, M., Stiller,
G., Van Roozendael, M., and Zhang, G.: Validation of MIPAS-
ENVISAT NO2 operational data, Atmos. Chem. Phys., 7, 3261–3284, 2007, http://www.atmos-chem-phys.net/7/3261/2007/.
Wiacek, A., Jones, N. B., Strong, K., Taylor, J. R., Mit-
termeier, R. L., and Fast, H.: First detection of meso-
thermospheric Nitric Oxide (NO) by ground-based FTIR so-
lar absorption spectroscopy, Geophys. Res. Lett., 33(L03), 811,
doi:10.1029/2005GL024897, 2006.
Wiacek, A., Taylor, J. R., Strong, K., Saari, R., Kerzenmacher, T.,
Jones, N. B., and Griffith, D. W. T.: Ground-Based solar absorp-
tion FTIR spectroscopy: characterization of retrievals and first
results from a novel optical design instrument at a New NDACC
Atmos. Chem. Phys., 8, 5801–5841, 2008 www.atmos-chem-phys.net/8/5801/2008/
8/2/2019 T. Kerzenmacher et al- Validation of NO2 and NO from the Atmospheric Chemistry Experiment (ACE)
http://slidepdf.com/reader/full/t-kerzenmacher-et-al-validation-of-no2-and-no-from-the-atmospheric-chemistry 41/41
T. Kerzenmacher et al.: Validation of NO2 and NO from ACE 5841
Complementary Station, J. Atmos. Oceanic Technol., 24, 432–
448, 2007.
Wolff, M. A., Kerzenmacher, T., Strong, K., Walker, K. A., Toohey,
M., Dupuy, E., Bernath, P., Boone, C., Brohede, S., Catoire, V.,
von Clarmann, T., Coffey, M., Daffer, W. H., Maziere, M. D.,
Duchatelet, P., Glatthor, N., Griffith, D. W. T., Hannigan, J.,
Hase, F., Hopfner, M., Huret, N., Jones, N., Jucks, K., Ka-
gawa, A., Kasai, Y., Kramer, I., Kullmann, H., Kuttippurath, J.,
Mahieu, E., Manney, G., McLinden, C., Mebarki, Y., Mikuteit,
S., Murtagh, D., Piccolo, C., Raspollini, P., Ridolfi, M., Ruhnke,
R., Santee, M., Senten, C., Smale, D., Tetard, C., Urban, J., and
Wood, S.: Validation of HNO3, ClONO2 and N2O5 from the At-
mospheric Chemistry Experiment Fourier Transform Spectrom-
eter (ACE-FTS), Atmos. Chem. Phys., 8, 3529–3526, 2008,
http://www.atmos-chem-phys.net/8/3529/2008/.
Wunch, D., Tingley, M. P., Shepherd, T. G., Drummond, J. R.,
Moore, G. W. K., and Strong, K.: Climatology and Predictabil-
ity of the Late Summer Stratospheric Zonal Wind Turnaround
over Vanscoy, Saskatchewan, Atmos.-Ocean, 43, 301–313,
doi:10.3137/ao.430402, 2005.